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A novel aldol reaction of alkenyl trichloroacetates with α-keto esters was realized by using dibutyltin dimethoxide as a catalyst, which was regenerated by the addition of methanol. The reaction was found to be remarkably accelerated by the addition of a catalytic amount of a bidentate phosphine⋅silver(I) complex. Use of the BINAP⋅silver triflate (AgOTf) complex as the chiral co-catalyst resulted in the formation of optically active aldol products possessing a chiral tertiary carbon with up to 93% ee. This catalytic method was further applied to the asymmetric reaction of diketene with methyl benzoylformate.

The safe operation of a semi-batch catalytic reactor remains a sensitive issue when highly exothermic side reactions may occur, and various elements such as controllability, stability, safety, and economic aspects have to be considered in the process development. Nominal operating conditions are set to avoid excessive thermal sensitivity to variations in the process parameters. Several shortcuts or model-based methods are used to estimate the safety limits and runaway boundaries for the operating variables. Among them, the Morbidelli & Varma (MV) generalized sensitivity criterion proved to be a powerful method for assessing the critical conditions of a chemical process. The approached case study concerns a semi-batch reactor used for the acetoacetylation of pyrrole with diketene in homogeneous liquid phase. The catalytic process is known to be of high risk because of the very exothermic side-reactions involving reactive diketene and, as a consequence, it requires rigorous control of the operating parameters. Previous studies tried to maximize the isothermal reactor performances by using various optimal feeding policies of the co-reactant under semi-empirically derived safety constraints. The present work illustrates how the runaway critical conditions can be precisely assessed and the safe operating region well established based on an extensive safety analysis and an adequate process model of reduced complexity. In addition, by screening the influential variables, the study also proves the close connection between the operating safety limits and the process kinetics/thermodynamics, initial/inlet and cooling conditions, offering a better support for the reactor optimization.

2-Alkenyl-6-methyl-4H-1,3-dioxin-4-ones, adducts of diketene to alkenals or alkenones, are useful synthons which are applicable to photocycloadditions to construct multiply-functionalized alicyclic compounds via stereoselective intramolecular path. Some of the cage-shaped photoproducts showed extraordinary spectroscopic features.

The reaction of Me2P(:X)H [X = O: 1; X = S: 2) with fluorinated ketones produced the α-hydroxy-phosphine oxides and sulfides, 3, 4 and 6. The reaction of Me2P(:O)CH2OH with formaldehyde gave the hemiacetal 7. Compound 2 reacted with formaldehyde and chloral to the corresponding α-hydrox-yphosphine sulfides, 8 and 9. The reaction of 2 with glyoxal furnished the 2: 1 addition product 10. In the case of diacetyl and benzil, the 1 : 1 addition products 11 and 12 were formed. The reaction of 2 with acetone and cyclohexanone produced in the same fashion 13 and 14. The reaction of 2 with pivaloyl chloride was found to occur with formation of the diphosphine monosulfide 15. In the case of benzoyl chloride, the 2: 1 addition-product 16 was formed Compound 1 reacted with diketene with formation of the α-hydroxy-bis(phosphine oxide) 17. The reaction of selected a-hydroxy-phosphine oxides and sulfides with different trimethylsilylating reagents produced the corresponding trimethylsilylated compounds, 18–23.

Cobalt(II) chloride catalyzes the acetylation of a variety of alcohols with acetic anhydride in excellent yield. Primary hydroxyl groups can be selectively acylated in the presence of secondary and tertiary ones while the secondary hydroxyl groups can be preferentially acetylated in the presence of tertiary ones. Tertiary alcohols have been found to give ketones, acetoacetates, olefins, and diketene in addition to the acetate

It was found that (2 + 2) cycloaddition reaction of diketene with Schiff bases was effectively promoted by imidazole as a catalyst to afford 3-acetyl-2-azetidinone derivatives 4. As an application of this new method, a practical asymmetric synthesis of 4 and its conversion into (3S,4S)-4-carboxy-1-(di-p-anisylmethyl)-3-[(R)-1-hydroxyethyl]-2- azetidinone, which is a key intermediate for the synthesis of carbapenem and penem antibiotics, were accomplished.

(-)-Tetrahydrolipstatin (1) has been synthesised starting from diketene using photoalkylation and s-lactone enolate alkylation as key steps.

In this work, two novel isocyanide-based multicomponent reactions of 1,2-diamine compounds with diketene have been developed as efficient strategies for the synthesis of 2,3,4,5-tetrahydro-1H-benzo[b][1,4]diazepine-2-carboxamides with regiochemical control and 1,6-dihydropyrazine-2,3-dicarbonitriles in good to excellent yields at ambient temperature.

In this work, 1,2,3,4,5,8-hexahydro-1,3,7-trimethyl-2,4-dioxopyrido[2,3-d]pyrimidine-6-carboxamide derivatives were synthesized in a simple and efficient method from the four-component condensation reaction of diketene, an aliphatic or aromatic amine, an aromatic aldehyde, and 6-amino-1,3-dimethyluracil in the presence of a catalytic amount of p-toluenesulfonic acid under mild conditions at ambient temperature in high yields.

A one-pot four-component reaction of an aliphatic or aromatic amine, diketene, an aromatic aldehyde and 1,3-diphenyl-1H-pyrazol-5-amine in the presence of p-toluenesulfonic acid as a catalyst has been developed. In this reaction, a new class of fully substituted pyrazolo[3,4-b]pyridine-5-carboxamide derivatives is produced under mild reaction conditions and in good yields at ambient temperature.

A convenient synthetic protocol was elaborated for creation of combinatorial libraries of 1-(R1-phenyl)-5-methyl-N-R2-1H-1,2,3-triazole-4-carboxamides. As starting materials, commercially available or readily prepared azides, amines, and diketene were selected for the reaction which has proceeded in a one-pot system with high yields and in short time.

This research's main goals were to analyze ketene dimers' relative stability and expand group additivity value (GAV) methodology for estimating the thermochemical properties of high-weight ketene polymers (up to tetramers). The CBS-Q multilevel procedure and statistical thermodynamics were used for calculating the thermochemical properties of 20 cyclic structures, such as diketenes, cyclobutane-1,3-diones, cyclobut-2-enones and pyran-4-ones, as well as 57 acyclic base compounds organized into five groups. According to theoretical heat of formation predictions, diketene was found to be thermodynamically favored over cyclobutane-1,3-dione and its enol-tautomeric form (3-hydroxycyclobut-2-enone). This result did not agree with old combustion experiments. 3-Hydroxycyclobut-2-enone was found to be the least stable dimer and its reported experimental detection in solution may have been due to solvent effects. Substituted diketenes had lower stability than substituted cyclobutane-1,3-diones with an increased number of methyl substituents, suggesting that cyclobutane-1,3-dione type dimers are the major products because of thermodynamic control of alkylketene dimerization. Missing GAVs for the ketene dimers and related structures were calculated through linear regression on the 57 acyclic base compounds. Corrections for non next neighbor interactions (such as gauche, eclipses, and internal hydrogen bond) were needed for obtaining a highly accurate and precise regression model. To the best of our knowledge, the hydrogen bond correction for GAV methodology is the first reported in the literature; this correction was correlated to MP2/6-31Gdagger and HF/6-31Gdagger derived geometries to facilitate its application. GAVs assessed by the linear regression model were able to reproduce acyclic compounds' theoretical thermochemical properties and experimental heat of formation for acetylacetone. Ring formation and substituent position corrections were calculated by consecutively replacing the GAVs regarding the 20 cyclic structures' thermochemical properties.

We report an inexpensive method for producing a diverse array of pyrrole amides on a large scale and in good yield. The synthetic sequence allows for the preparation of a number of pyrrole amide derivatives in excellent to moderate yields from commercially available compounds. The diketene adduct, in the presence of an amine nucleophile, provides an excellent method for acetoacetylation. For diversity and versatility, a second method utilizing Meldrum's acid was successfully employed for the preparation of additional acetoacetamide derivatives. Using the Knorr pyrrole synthesis, pyrrole amides were readily prepared from the oxime of the acetoacetamides.

A convenient synthetic protocol was elaborated for creation of combinatorial libraries of 1-(R(1)-phenyl)-5-methyl-N-R(2)-1H-1,2,3-triazole-4-carboxamides. As starting materials, commercially available or readily prepared azides, amines, and diketene were selected for the reaction which has proceeded in a one-pot system with high yields and in short time.

Using diketene as a basic reagent, a one-pot, pseudo-five-component reaction for the synthesis of highly substituted bisfuramides is described. In this method, ring opening of diketene occurs in mild condition and without a catalyst. Thus, the reaction between diketene, 1,n-diamine, and dibenzoylacetylene, in the presence of triphenylphosphine, produces bisfuramides.

In this work, 1,2,3,4,5,8-hexahydro-1,3,7-trimethyl-2,4-dioxopyrido[2,3-d]pyrimidine-6-carboxamide derivatives were synthesized in a simple and efficient method from the four-component condensation reaction of diketene, an aliphatic or aromatic amine, an aromatic aldehyde, and 6-amino-1,3-dimethyluracil in the presence of a catalytic amount of p-toluenesulfonic acid under mild conditions at ambient temperature in high yields.

The thermal reaction of HNCO has been studied in a static cell at temperatures between 873 and 1220 K and a constant pressure of 800 torr under highly diluted conditions. The reaction was measurable above 1000 K by FTIR spectrometry. The products detected include CO, CO2, HCN, NH3, and the unreacted HNCO. In this moderate temperature regime, the rates of product formation and HNCO decay cannot be accounted for by a previously established high-temperature mechanism, assuming HNCO NH + CO (1) as the initiation process. Instead, a new bimolecular reaction, 2HNCO CO2 + HNCNH (2), has been invoked to interpret the disappearance of HNCO as well as the formation of various products, most importantly CO2. The concentration profiles of all measured species can be quantitatively modeled, throughout the temperature range analyzed, by varying k2 using a modified mechanism. The kinetically modeled values of k2 can be effectively represented by This result agrees closely with that computed with the conventional transition-state theory using the TST parameters predicted by the BAC-MP4 method: The bimolecular reaction takes place via a stable 4-membered ring intermediate which is isoelectronic with diketene; viz.

Ab initio quantum mechanical methods have been used to study the dimerization of ketene to form diketene and 1,3-cyclobutanedione. Molecular structures for reactants, products, and transition states of the above reactions have been determined at the self-consistent-field (SCF) level of theory with a double-ζ plus polarization (DZ+P) basis set. Relative energies of stationary points have been predicted at the single and double excitation configuration interaction (CISD) level of theory. At the DZ+P SCF level of theory, the formation of 1,3-cyclobutanedione is predicted to proceed through an unsymmetrical transition state and has a classical barrier height of 36 kcal/mol. The formation of diketene also proceeds through an unsymmetrical transition state and is predicted to have a barrier height of 32 kcal/mol. Inclusion of electron correlation and zero-point vibrational energy yields an estimate of 26 kcal/mol for the latter barrier. Neither transition state is consistent with the 2S+2A cycloaddition reaction mechanism

Ab initio calculations of deuterium isotope ratios in the formation of diketene agree with natural deuterium abundances reported for this molecule

One family of poly (ortho esters) can be prepared by the reaction of diketene acetals and diols. This polymer has recently been used in the development of bioerodible implants for the release of the antineoplastic agent 5-fluorouracil (5-FU) and the narcotic antagonist naltrexone. Polymer erosion was found to depend on both the nature of the acidic excipient used to control erosion rate and on the composition of the polymer. Good control over rate of release of 5-FU was achieved by using suberic acid and a polymer based on 1,6-hexanediol. Preliminary encouraging survival times have been obtained with mice inoculated with IL1210 leukaemia. Polymers with a 50 wt% loading of naltrexone pamoate have been shown to release the drug by good zero order kinetics and in vivo studies are currently in progress. Another family of poly (ortho esters) can be prepared by a transesterification reaction between a triol and a trialkyl ortho ester. When the transesterification reaction is carried out with flexible triols such as 1,2,6-hexanetriol, ointment-like materials are obtained even though molecular weight can be in excess of 50,000. Release of therapeutic agents from such ointments can also be controlled with acidic excipients. Such materials are particularly useful for peptide release because these can be incorporated into the polymer at room temperature without the use of solvents. Preliminary indications of retention of activity have been obtained.

Diketene undergoes a VO(OR)Cl2-induced cyclization with styrenes via ring opening to give 3-alkoxycarbonyl-2-methyl-5-phenyl-4,5-dihydrofurans. Desilylative aromatization to the furans is observed in the reaction with α-triemthylsilylstyrene.

The one-pot synthesis of highly substituted piperid-4-ones has been achieved. Diketene is added to a tosyl imine in the presence of TiCl4 and MeOH, followed by 1 equiv of aldehyde to generate 2,6-disubstituted nonsymmetrical piperid-4-ones as a mixture of cis-/trans-diastereomers in good yields. This mixture of diastereomers can be converted to a single 2,6-cis-diastereomer by epimerization with K2CO3.

A four-component reaction for the synthesis of 1,2-dihydroisoquinoline derivatives is described. The Huisgen 1,4-dipolar intermediate, which is produced from isoquinoline and an electron-deficient acetylene compound 1, reacts with H2O in the presence of diketene to produce 1,2-dihydroisoquinoline derivatives 2 (Scheme 1). In addition, reaction of isoquinoline, dibenzoylacetylene (=1,4-diphenylbut-2-yne-1,4-dione), and diketene in the presence of H2O leads to pyrroloisoquinoline derivative 7. The structures of the compounds 2a–f and 7 were corroborated spectroscopically (IR, 1H- and 13C-NMR, EI-MS) and by elemental analyses. A plausible mechanism for the reaction is proposed (Schemes 2 and 3).

The alkylating potential of diketene (4-methylene-2-oxetanone), the basic unit of many derivatives of pesticides, chemicals, pharmaceuticals, and dyestuffs, was investigated kinetically. The nucleophile 4-( p-nitrobenzyl)pyridine (NBP), a trap for alkylating agents with nucleophilic characteristics similar to DNA bases, was used as an alkylation substrate. The alkylation reactions were performed in water/dioxane solvent mixtures. To gain insight into the effect of the hydrolysis of diketene on its alkylating efficiency, alkylation and competing hydrolysis were studied in parallel. Conclusions were drawn as follows: (i) Although diketene, unlike other four-membered ring lactones, is inactive as a carcinogen in experimental animals, it shows an alkylating potential of about 2 orders of magnitude higher than beta-propiolactone or beta-butyrolactone, which are classified as possibly carcinogenic to humans by the IARC. (ii) The reactivity of diketene as an alkylating agent is enthalpy-controlled. (iii) The fact that the hydrolysis reaction of diketene is slightly faster than those of other four-membered ring lactones shows that diketene is more efficient than beta-propiolactone or beta-butyrolactone as an alkylating agent, since the hydrolysis of this species poses less competition to the alkylation reaction. (iv) Diketene undergoes acyl fission in the alkylation reaction, which results in an amide bond in the NBP-diketene adduct. The lability of the amide bond as opposed to the amine bonds formed by beta-propiolactone and beta-butyrolactone could be one of the differential factors responsible for the lack of carcinogenicity of diketene. (v) Ab initio calculations of the energy barriers help to understand the unusual reactivity of diketene.

The one-pot synthesis of highly functionalized pyrrole derivatives from the reaction of an enaminone, which can be derived from the reaction between two primary amines and diketene, in the presence of nitrostyrene is described. The reaction occurred under neutral conditions and in excellent yields.

An effective route to functionalized 4,5-dihydro-1H-pyrrol-3-carboxamide derivatives is described. This involves reaction of N-alkyl-3-oxobutanamides, which result from the addition of an amine to the diketene, and a primary amine in the presence of dibenzoylacetylene. The 1,3-dicarbonyl compounds obtained from the addition of an amine to diketene were trapped with a primary amine to produce (Z)-3-(alkylamino)-N1-alkyl-2-butenamide, which reacts with dibenzoylacetylene to produce 4,5-dihydro-1H-pyrrol-3-carboxamide derivatives.

An effective route to functionalized 1,2,3,10b-tetrahydropyrrolo[2,1- A]isoquinoline-1-carboxamide derivatives is described. This involves reaction of N-alkyl-3-oxobutanamides, which result from the addition of amines to diketene, and dibenzoyl-acetylene in the presence of isoquinoline. The reactive 1:1 intermediate obtained from the addition of isoquinoline to diben-zoyl--acetylene is trapped by OH acids such as N-alkyl-3-oxobutan-amides to produce the pyrrolo[2,1- A]isoquinoline-1-carboxamide derivatives.

At the present time, three poly(ortho ester) systems have been described. The first one was developed at the Alza Corporation and is prepared by the transesterification reaction between a diol and diethoxytetrahydrofuran. It is currently marketed under the trade name of Alzamer®. A second poly(ortho ester) system, developed at SRI International, is prepared by the addition of polyols to the diketene acetal 3,9 bis (ethylidene 2,4,8,10 tetraoxaspiro [5,5] undecane). A third poly (ortho ester) system, also developed at SRI International, is prepared by a transesterification reaction between a triol and an ortho ester, followed by self-condensation of the reaction product. Major utility of poly(ortho esters) as bioerodible drug delivery devices resides in their acid sensitivity which allows preparation of devices with lifetimes ranging from hours to many months by using acidic or basic excipients physically incorporated into the matrix.

Acylation of the carboline derivatives 6 and 9 with diketene affords the corresponding N-(acetoacetyl)carbolines 7 and 10, respectively. While 10 can be converted into a 1:2.1 mixture of the title compounds 11 a and 11 b on treatment with oxalic acid, the cyclic acetal 7 can only be cyclized to yield the pyridone derivative 8. Michael addition of methyl malonate to the unsaturated ketone 11 b proceeds with excellent stereoselectivity to generate the keto diester 12 a which, on treatment with a base is transformed into its diastereoisomer 12 b. In contrast to 11 b, its stereoisomer 11 a does not react with methyl malonate.

A gas chromatographic method was developed, based on a reference standard, for analysis of the reactive diketene acetal 3,9-diethylidene-2,4,8,10-tetraoxaspiro[5.5]undecane (DETOSU). The method is based on the conversion of DETOSU to 3,9-diethyl-3,9-dimethoxy-2,4,8,10-tetraoxaspiro[5.5]undecane, a stable ortho ester.

An effective route to functionalized furamide derivatives is described. This involves reaction of N -alkyl-3-oxobutanamides, derived from the addition of amines to the diketene, and dibenzoylacetylene in the presence of triphenylphosphoine. The reactive 1:1 intermediate obtained from the addition of triphenylphosphine to dibenzoylacetylene was trapped by OH-acids such as N -alkyl-3-oxobutanamide to produce functionalized furamide derivatives.

Illustrative discussion is made in chronological order on six select catalysts for asymmetric carbon−carbon bond formations that are scalable and are reported to be potentially scalable: (1) thiamine diphosphate (TPP)-bound pyruvate decarboxylase (PDC) used in the industrial production of (R)-l-phenyl acetyl carbinol (PAC; 5); (2) bimetallic Lewis acid−Bronsted base catalyst (9) for asymmetric Michael addition of dialkyl malonates; (3) Lewis acid−Lewis base catalyst (11) for asymmetric cyanosilylation of aryl alkyl ketones; (4) a chiral Schiff base chelated titanium(IV) alkoxide catalyst (32) for asymmetric addition of diketene to aldehydes; (5) 2-deoxyribose-5-phosphate aldolase (DERA) used in the preparation of (3R,5S)-6-chloro-2,4,6-trideoxy-erythro-hexose in its lactol form (50) from acetaldehyde (43)/chloroacetaldehyde (47) (2:1); and (6) chiral C2-symmetric quaternary ammonium bromides, such as 63 of an N-spiro type, for asymmetric alkylation of Schiff bases of glycine and α-substituted glycine der...

(1a; R = Et) [638-07-3] C6H9ClO3 (MW 164.60) InChI = 1S/C6H9ClO3/c1-2-10-6(9)3-5(8)4-7/h2-4H2,1H3 InChIKey = OHLRLMWUFVDREV-UHFFFAOYSA-N (1b; R = Me) [32807-28-6] C5H7ClO3 (MW 150.57) InChI = 1S/C5H7ClO3/c1-9-5(8)2-4(7)3-6/h2-3H2,1H3 InChIKey = HFLMYYLFSNEOOT-UHFFFAOYSA-N (1c; R = i-Pr) [41051-20-1] C7H11ClO3 (MW 178.63) InChI = 1S/C7H11ClO3/c1-5(2)11-7(10)3-6(9)4-8/h5H,3-4H2,1-2H3 InChIKey = GSNGPDOWIOPXDR-UHFFFAOYSA-N (1d; R = t-Bu) [74530-56-6] C8H13ClO3 (MW 192.66) InChI = 1S/C8H13ClO3/c1-8(2,3)12-7(11)4-6(10)5-9/h4-5H2,1-3H3 InChIKey = DVOUIKQENBFPRS-UHFFFAOYSA-N (highly functionalized four-carbon building block for organic synthesis1) Physical Data: (1a) mp −8.5 °C; bp 95 °C/10 mmHg; fp 92 °C; d 1.212 g cm−3. (1b) mp 14 °C; bp 50 °C/1 mmHg; fp 107 °C; d 1.287 g cm−3. (1c) mp 10 °C; bp 64 °C/1.65 mmHg; fp 86 °C; d 1.152 g cm−3. (1d) bp 101 °C/15 mmHg; fp 41 °C; d 1.130 g cm−3. Form Supplied in: the alkyl 4-chloroacetoacetates are colorless liquids. Solubility: sol most organic solvents. The ethyl ester (1a) is 12% enolized in the pure liquid, and highly enolized (60% in CCl4) in nonpolar solvents.2 Preparative Methods: the industrial production of the esters is made exclusively by chlorination of Diketene followed by reaction of the intermediate acid chloride with the corresponding alcohol.3 Handling, Storage, and Precautions: these reagents are lachrymators of moderate toxicity; use in a fume hood.

[5394-63-8] C7H10O3 (MW 142.17) InChI = 1S/C7H10O3/c1-5-4-6(8)10-7(2,3)9-5/h4H,1-3H3 InChIKey = XFRBXZCBOYNMJP-UHFFFAOYSA-N (acetylketene equivalent, used for acetoacetylation and cycloaddition reactions; can be functionalized to provide substituted acylketenes; diketene equivalent) Alternate Name: diketene–acetone adduct. Physical Data: mp 12–13 °C; bp 65–67 °C/0.2 mmHg; d 1.088 g cm−3. Solubility: miscible with most organic solvents. Form Supplied in: neat liquid; 95% (major impurity acetone). Analysis of Reagent Purity: GC (keep injector port 200–225 °C); NMR. Preparative Methods: the diketene–acetone adduct 1 is one of a series of 1,3-dioxin-4-ones which can be prepared by the reaction of diketene with an aldehyde or ketone in the presence of an acidic catalyst2 or a quaternary ammonium salt (eq 1).3 An alternate preparatory method is the reaction of a β-keto acid with acetone.4 (1) Purification: high-vacuum distillation at temperatures below 80 °C. Handling, Storage, and Precautions: generally nonhazardous; anticipate release of acetone upon heating over 80 °C; will also produce CO2 if heated in presence of water; extremely good solvent: will dissolve some plastic tubing. Use in a fume hood.

Starting from one stereogenic center (in this case from l -serine), we obtained two chiral Schiff bases possessing oxazoline moieties, each of which recognized a different enantioface of aldehydes with a high enantiomeric excess [up to 93% ee ( R ) and 89% ee ( S )] in the addition reaction of diketene to 2-furfural.

A procedure was developed for the stereoselective synthesis of aminated derivatives of (+)-1-{(1R,3R,6S)-4,7,7-trimethylbicyclo[4.1.0]hept-4-en-3-yl}ethan-1-one. The configuration of the side-chain chiral center in (+)-1-{(1R,3R,6S)-4,7,7-trimethylbicyclo[4.1.0]hept-4-en-3-yl}ethan-1-ol was determined by X-ray analysis. Diketene and Meldrum’s acid were proposed as initial compounds for the synthesis of, respectively, 3-oxobutanoic and malonic acid esters having a 1-ethyl-4,7,7-trimethylbicyclo[4.1.0]hept-4-ene fragment.

A new variation of poly(ortho ester)s prepared by the addition of diols to the diketene acetal 3,9-diethylidene-2,4,8,10-tetraoxaspiro[5.5]undecane is described. In this variation, a short segment ...

Synthesis of [5-methyl-3H]-nitrendipine by means of a new method was described. Methyl-[3H]-methanol was reacted with diketene forming methyl-[3H]acetoacetate, followed by treatment with ammonia to give [methyl-3H]-3-aminoacrotonate, which was reacted with methyl 2-[(3-nitrophenyl)-3-methylene]-3-oxobutanoate to synthesize [5-methyl-3H]-nitrendipine. Its specific activity and radiochemical purify were 23 Ci/mmol and >98%, respectively. © 1997 John Wiley & Sons, Ltd.

An aldol‐type reaction catalyzed by a Ti‐(S)‐BINOL complex using with a diketene as substrate is described herein. The complex derived from 1.0 molar equivalent of Ti(O‐i‐Pr)4 and 2.0 molar equivalents of (S)‐BINOL gave (S)‐isopropyl 5‐hydroxy‐7‐phenyl‐3‐oxo‐6‐heptenoate with high enantioselectivity.

Knoevenagel-type reaction between diketene and aldehydes proceeded in the presence of Ti(O- i -Pr) 4 . This reaction proceeded via titanium enolate derived from Ti(O- i -Pr) 4 and diketene. As for the stereoselectivity of the products, E -isomers were produced predominantly in the case of aromatic aldehydes.

[70639-89-3] C9H18O2Si (MW 186.11) InChI = 1S/C9H18O2Si/c1-8(6-9(10)11-2)7-12(3,4)5/h1,6-7H2,2-5H3 InChIKey = DPBRXLFGMUIBMC-UHFFFAOYSA-N (isoprenoid acid synthon which reacts readily with a variety of electrophiles) Physical Data: pale-yellow oil; bp for precursor acid 53 °C/0.01 Torr.1, 2 Solubility: soluble in all common organic solvents. Analysis of Reagent Purity: the precursor acid has been characterized by 1H NMR and IR spectroscopies.1, 2 Preparative Methods: readily prepared by reaction of diketene with trimethylsilylmethylmagnesium chloride in the presence of a Ni(II) catalyst,1, 2 followed by esterification of the resulting acid using diazomethane.3 Purification: distillation at reduced pressure. Handling, Storage, and Precautions: should be stored at or below room temperature away from acids and other electrophilic species.