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An effective synthesis of four potentially biologically active O- and N-containing 23-, 28-, 30-, and 31-membered macroheterocycles from undec-10-enal was carried out. First, undec-10-enal was converted to undec-10-enyl undec-10-enoate via the Tishchenko disproportionation reaction catalyzed by Al(i-PrO)3. The subsequent Wacker–Tsuji oxidation of undec-10-enyl undec-10-enoate gave 10-oxoundecanyl 10-oxoundecanoate. Finally, the [1+1]-condensation of 10-oxoundecanyl-10-oxoundecenoate with hydrazine hydrate or malonic, glutaric, or adipic acid dihydrazides resulted in the synthesis of four macroheterocycles. [ABSTRACT FROM AUTHOR]

Data on the influence of solvents, ratios and nature of reagents on the distribution of typical impurities and yields of target products of the reaction of 19-norpregna-1,3,5(10),16-tetraen-20-one derivatives with 4-dimethylamino-, 3,4-dimethoxy-, and 4-bromobenz-aldehydes and 3-pyridinecarbaldehyde were studied and summarized. A mechanism for the formation of 1,3-diketones in the reaction of 17-acetyl-substituted steroids with 4-dimethyl-aminobenzaldehyde in the presence of lithium diisopropylamide in THF was proposed. The Claisen-Schmidt condensation results were shown to be critically affected by the base and the steroid solubility. Optimization possibilities were considered and an improved procedure for the synthesis of new 21-benzylidene-substituted steroids was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] Ethanol over calcium stannate (CaSnO 3) catalyst under supercritical conditions (400 °C, 120 atm) is transformed mainly into ethanal, ethyl acetate and 2-buten-1-ol. The process is accompanied by crystallization of the amorphous catalyst. [ABSTRACT FROM AUTHOR]

Tishchenko reaction is the dimerization of two molecules of an aldehyde to produce symmetrical esters. These esters find wide applications in many reactions in organic synthesis. A variant of this reaction, the Evans‐Tishchenko reaction, catalyzed by SmI2 affords 1,3‐anti‐diol monoesters. This chemistry has found wide applications in natural product synthesis as it offers a mild and efficient methodology for the formation of 1,3‐diols stereoselectively. In this review, we mainly focus on recent advancements in the transition metal catalyzed and lanthanide‐actinide catalyzed Tishchenko reactions and their applications in organic synthesis covering literature from 2014 to 2019. [ABSTRACT FROM AUTHOR]

A new family of benzimdazolin-2-iminato actinide−(IV) complexes [(Bim 7-Me Dipp/Me N)An(N(SiMe 3 ) 2 ) 3 ] (An = U ( 3 ), Th ( 4 )) and [(Bim 4-Me Dipp/Me N)An(N(SiMe 3 ) 2 ) 3 ] (An = U ( 5 ), Th ( 6 )) were synthesized and their solid state structures were established by single-crystal X-ray diffraction analysis. The catalytic performances of complexes 3 – 6 towards the homo- and cross-coupling of aldehydes (Tishchenko reaction) were studied and the thorium complexes 4 and 6 displayed moderate to high activities for the production of the corresponding symmetric and unsymmetrical esters. Coupling of aldehyde and alcohols, known as the tandem proton-transfer esterification, and the intermolecular coupling reaction between aldehyde and trifluoromethylketones were also investigated by these thorium complexes, indicating a complementary method to obtain unsymmetrical esters selectively. Plausible mechanisms for these reactions are proposed based on stoichiometric studies. [ABSTRACT FROM AUTHOR]

The catalytic asymmetric synthesis of (−)-arctigenin is reported. The central optically pure lactone intermediate is obtained either from an Ir-catalyzed asymmetric Tishchenko reaction or an asymmetric oxidative lactonization and subsequently converted to β-iodomethyl-α-methylene-γ-butyrolactone. Several recent Negishi coupling protocols were investigated for the introduction of an aryl unit in the presence of the α-methylene-γ-butyrolactone. The introduction of a second aryl unit was achieved using a diastereoselective Rh-catalyzed conjugate addition and protonation under protecting-group-free conditions. [Display omitted] [ABSTRACT FROM AUTHOR]

Four aluminum alkoxide complexes containing β-hydroxy-imino ligands, [(2,6-Me 2 C 6 H 3 )NCPhCH 2 CPh 2 O] 2 AlMe ( 3a ), [(2,6- i Pr 2 C 6 H 3 )NCPhCH 2 CPh 2 O] 2 AlMe ( 3b ), [(2,6-Me 2 C 6 H 3 )NCPhCH 2 C(C 12 H 8 )OAlMe 2 ] 2 ( 3c ) and [(2,6- i Pr 2 C 6 H 3 )NCPhCH 2 C(C 12 H 8 )OAlMe 2 ] 2 ( 3d ) were synthesized in high yields, and their structural features were provided. The catalytic behavior of those four complexes about the Tishchenko reaction with a range of aromatic aldehydes as substrates were assessed, and it present a synthetically useful protocol to the solvent-free Tishchenko reaction under mild conditions. [ABSTRACT FROM AUTHOR]

Deprotonolysis of the N,O-bidentate pyridyl functionalized alkoxy ligands, 1,1-dimethyl-2-(pyridin-2-yl)ethanol ( LH), 1-phenyl-2-(pyridin-2-yl)ethanol ( LH) and 1,1-diphenyl-2-(pyridin-2-yl)ethanol ( LH), with 1 equiv of AlMe gave the corresponding dimeric metal-monoalkyl compounds [ LAlMe] ( 1), [ LAlMe] ( 2), and [ LAlMe] ( 3), respectively. Compounds 1- 3 were characterized by H and C NMR spectroscopy analysis, and the molecular structures of 1 and 2 were further confirmed by X-ray diffraction analysis. In the presence of PrOH, aluminum compounds 1- 2 exhibited excellent catalytic activity for the solvent-free Tishchenko reaction under mild conditions. In addition, the catalyst 3 can be easily isolated and recycled three times without a significant decrease in activity. [ABSTRACT FROM AUTHOR]

Bulky guanidinate stabilized homoleptic complexes of [LM(thf) n L] [L = {ArNC (N i Pr 2 )NAr} (Ar = 2,6- Me 2 –C 6 H 3 )]; M = Mg, Ca, and Zn; n = 0–1) have been synthesized with three different synthetic routes. First, treatment of bis{bis(trimethylsilyl)amide}s of Mg, Ca, and Zn i.e. [M{(N(SiMe 3 ) 2 } 2 ] (M = Mg, Ca(thf) 2 , and Zn) with free guanidine ligand (LH) at 80 ° C, elimination of NH(SiMe 3 ) 2 and formation of [LM(thf) n L] (M = Mg, Ca and Zn; n = 0–1) ( 3 – 5 ) complexes were occurred. Second, the reaction of two equivalents of potassium salt of LH with metal dihalides via salt metathesis led to the formation of homoleptic complexes. Third, the reaction between MR 2 (M = Mg, Ca, Zn; R = alkyl or OTf) and LH at reflux temperature, formation of bis(guanidinate) magnesium, calcium, and zinc complexes have been observed. The solid state structures of LH( 1 ), LK( 2 ) and all three bis(guanidinate) magnesium, calcium and zinc complexes ( 3 – 5 ) were confirmed by X-ray structural analysis. Furthermore, dimerization of a range of aromatic, heteroaromatic and aliphatic aldehydes (Tishchenko reaction) has been demonstrated by using catalysts 3 – 5 . [ABSTRACT FROM AUTHOR]

The dimerization of aldehydes to the analogous carboxylic esters (Tischenko reaction) has been achieved in impressive yields using the dilithium compounds containing bidentate di-anionic pyrrolyl ligands as initiators. The initiated intermediate {[2-( t BuNCH)C 4 H 3 NLi][PhCH 2 OLi(TMEDA)]} 2 was isolated and characterized by satisfactory C, H and N microanalysis, 1 H, 13 C{ 1 H} and 7 Li NMR spectra in pyridine-d 5 at ambient temperature, and single crystal X-ray structural data. The processes involve a redox reaction of 2-aminopyrrolyl dilithium compound with aldehyde. [ABSTRACT FROM AUTHOR]

Three amidinatoaluminum compounds, [{MeC(NCy) 2 }AlMe(μ-OMe)] 2 ( 1 ), [{(PhN)MeC(NCy)}AlMe(μ-OMe)] 2 ( 2 ) and [{(PhN)MeC(N t Bu)}AlMe(μ-OMe)] 2 ( 3 ), were prepared by the insertion reaction of oxygen with the corresponding aluminum amidinate in high yield and characterized by 1 H and 13 C NMR spectra and single crystal X-ray diffraction analysis. 1 – 3 were used as pre-catalysts to catalyze the Tishchenko reaction and both 2 and 3 exhibited good to excellent catalytic activity under mild conditions. [ABSTRACT FROM AUTHOR]

Redox transmetallation/protolysis reactions were employed to synthesize a series of the rare earth bis(aryl)formamidinate complexes. Trivalent complexes were synthesized with three chelating formamidinate ligands about the metal centers. A study of the reactivity towards the Tishchenko reaction shows the compounds catalyse the Tishchenko reaction in the formation of esters from aldehydes. [Display omitted] • The chemistry we present here extends our studies of rare earth formamidinato chemistry and their applicability in Tishchenko catalysis. • The chemistry presented should be of great interest to inorganic and organometallic chemists, and more specifically to those with interests in f-block chemistry. Furthermore, due to the great interest in cyclopentadienyl replacement chemistry in rare earth studies more broadly, this chemistry will appeal to most synthetic and structural chemists. • We therefore think that Inorganica Chmica Acta is the right platform to publish our results to rapidly spread our findings to the inorganic chemical community. • We look forward to hearing from you soon regarding this submission. Redox transmetallation/protolysis reactions of rare earth metals, Hg(C 6 F 5) 2 and a formamidine (PhFormH = N , N '-(diphenyl)formamidine or DMFormH = N , N ' -bis(2,4-dimethylphenyl)formamidine) in tetrahydrofuran (thf) or 1,2-dimethoxyethane (dme) were employed to synthesize a series of the rare earth N,N' -bis(aryl)formamidinate complexes. Accordingly, trivalent complexes with the composition [Ln(PhForm) 3 (thf) n ]⋅(solv.) m [n = 2, m = 0, Ln = La (1), Pr (2); n = 2, m = 0.5, solv = thf, Sm (3); n = 2, m = 1.5, solv. = PhMe, Ln = Nd (4); n = 2, m = 1.5, solv. = thf, Ln = Gd (5); n = 2, m = 3, solv. = thf, Ln = Tb (6), Dy (7), and Y (8); n = 1; m = 0, Ln = Ho (9), Er (10) and Lu (11)] or [Ln(DMForm) 3 (solv.)] [Ln = Sm (12), Gd (13), solv. = dme; Ln = Pr (14), Ho (15), solv. = DMFormH; Ln = Y (16), Lu (17), solv. = thf; Ln = Er (18), solv. = dmf; dmf = N,N -dimethylformamide] were synthesized and characterized by X-ray crystallography. Complexes 1 – 8 have eight coordinate Ln metals with three chelating PhForm and two transoid thf ligands, whilst 9 – 11 are seven coordinate with a single thf ligand. Thus, there are three structural discontinuities, namely at Ho, Y, Er, the second of which occurs in defiance of a decrease in ion size. An investigation of catalytic reactivity of representative Ln complexes in the conversion of aldehydes into esters (Tishchenko reaction) revealed most have modest catalytic properties. [Y(PhForm) 3 (thf) 2 ]⋅3thf 7 and [Y(DMForm) 3 (thf)] 16 had the highest reactivity for their respective ligands, with 16 by far the most effective catalyst. [ABSTRACT FROM AUTHOR]

The thiolate-catalyzed Tishchenko reaction has shown high chemoselectivity for the formation of double aromatic-substituted esters. In the present study, the detailed reaction mechanism and, in particular, the origin of the observed high chemoselectivity, have been studied with DFT calculations. The catalytic cycle mainly consisted of three steps: 1,2-addition, hydride transfer, and acyl transfer steps. The calculation results reproduce the experimental observations that 4-chlorobenzaldehyde acts as the hydrogen donor (carbonyl part in the ester product), while 2-methoxybenzaldehyde acts as the hydrogen acceptor (alcohol part in the product). The two main factors are responsible for such chemoselectivity: 1) in the rate-determining hydride transfer step, the para-chloride substituent facilitates the hydride-donating process by weakening the steric hindrance, and 2) the ortho-methoxy substituent facilitates the hydride-accepting process by stabilizing the magnesium center (by compensating for the electron deficiency). [ABSTRACT FROM AUTHOR]

Gas phase reactions of the substituted phenide ions with methyl formate have been studied. It was found that the results of these reactions depend mainly on the basicity of the phenide ion, which is related to the presence of the electron-accepting or electron-donating substituents in the benzene ring. It was shown that the phenide ions substituted with electron-withdrawing groups react with methyl formate in the gas phase in a two-step reaction. The first step that proceeds according to the typical addition-elimination mechanism results in the formation of the anion of the respective benzaldehyde derivative with the negative charge located either in the aldehyde group (acyl anion) or in the benzene ring (phenide anion) in position ortho to an aldehyde moiety. In the second step, the preliminary-formed anion reacts with the second molecule of methyl formate yielding formally product of the second addition-elimination reaction. Theoretical calculations as well as collision induced dissociation spectra of the model compounds suggest that this reaction proceeds according to the Tishchenko reaction mechanism yielding the respective phthalide anion. According to our knowledge, this is the first example of the Tishchenko-type reaction in the gas phase. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Mechanistic studies have been performed for the recently developed, Ni-catalysed selective cross-coupling reaction between aryl and alkyl aldehydes. A mono-carbonyl activation (MCA) mechanism (in which one of the carbonyl groups is activated by oxidative addition) was found to be the most favourable pathway, and the rate-determining step is oxidative addition. Analysing the origin of the observed cross-coupling selectivity, we found the most favourable carbonyl activation step requires both coordination of the aryl aldehyde and oxidative addition of the alkyl aldehyde. Therefore, the stronger π-accepting ability of the aryl aldehyde (relative to alkyl aldehyde) and the ease of oxidative addition of the alkyl aldehyde (relative to aryl aldehyde) are responsible for the cross-coupling selectivity. [ABSTRACT FROM AUTHOR]

A samarium-mediated novel synthesis of enantiopure 4-amino-1,3-diols is carried out through a samarium-promoted aldol-Tishchenko reaction starting from chiral α′-amino-α-chloro ketones (derived from natural α-amino acids) and aldehydes. The process takes place with moderate levels of stereoselectivity and in high yields. A mechanism is proposed to explain these results while the absolute configuration and structure of the aldol-Tishchenko adducts were established by X-ray analysis. This method has also been utilized for the synthesis of enigmols, 1-deoxysphingoid base analogues. [ABSTRACT FROM AUTHOR]

Reaction of homoleptic yttrium tris-alkyl complex YR3 (R=CH2C6H4NMe2-o) with 1 equivalent of amine bis(phenol)s LH2 (L=Me2NCH2CH2N(CH2-(2-O-C6H2-But2-3,5))2) afforded the solvent-free yttrium alkyl complex LYR (1), which has been characterized with elemental analysis, 1H NMR and IR spectra, and structural determination. The coordination geometry around the center metal atom can be best described as a distorted octahedron. It was found that complex 1 can be used as an efficient catalyst for the Tishchenko reaction. [ABSTRACT FROM AUTHOR]

Abstract: Aliphatic aldehydes react with catalytic amount of Dibal-H in n-pentane to give the corresponding Tishchenko products in good to excellent yields. On contrary, α-silyloxy aldehydes give α-silyloxy ketones via Oppenauer oxidation under similar condition. Tishchenko reaction of ω-alkene aldehydes followed by RCM and hydrogenation affords a convenient method to prepare the 11–37 membered macrocyclic lactones. [Copyright &y& Elsevier]

The development of solid strong base catalysts utilizable in green but acidic medium of scCO2 is reviewed. The strong base sites on mesoporous alumina and sulfated mesoporous alumina that had been generated by severe treatment at 773 K under vacuum (10−4 Torr) were not neutralized by the compressed Lewis acidic molecules of CO2, promoting a representative strong base-catalyzed reaction of the Tishchenko reaction as well as a typical base-catalyzed reaction of the Knoevenagel reaction in scCO2. Infrared spectroscopy of the adsorbed pyrrole, temperature-programmed desorption of CO2, and the poisoning by a very weak Brönsted acid of methanol have revealed that the average strengths of the base sites on mesoporous alumina and sulfated mesoporous alumina are weaker than that on conventional γ-alumina like JRC-ALO-4, but that they have a small number of strong base sites which function even in scCO2 medium. It was found that the addition of a slight amount of THF cosolvent into scCO2 remarkably accelerates the Tishchenko reaction over sulfated mesoporous alumina; the reaction rate in the scCO2–THF medium was 1.5-fold and 2-fold faster than those in ordinary organic solvents such as benzene and THF and that in pure scCO2, respectively. The unique structures of mesoporous alumina and sulfated mesoporous alumina have been fully characterized by N2 adsorption–desorption measurements and XRD analyses. [ABSTRACT FROM AUTHOR]

Abstract: Tishchenko reaction of benzaldehyde was carried out over the MgO whose surface O atoms were enriched with 18O to examine whether the surface O atoms of MgO are incorporated into the product and reactant. The surface lattice 18O atoms were incorporated in both the product and reactant. The 18O concentration was significantly higher for the product than for the reactant. In addition, the 18O in the product ester was located not only in the carbonyl group (Cso in the bridging position (Ch name="sbnd" />C); 18O exchange between benzaldehyde and MgO surface occurred not only in the adsorption–desorption of benzaldehyde, but also in the dimerization process. The oxygen exchange results in the migration of active sites of coordinative unsaturated site (CUS) over the surface of MgO catalyst during the reaction. [Copyright &y& Elsevier]

Abstract: Treatment of mesoporous silicate SBA-15 with Sm[N(SiMe3)2]3 led to the formation of a novel organolanthanide/inorganic hybrid material [SBA-15]Sm[N(SiMe3)2] x via abstraction of N(SiMe3)2 by terminal silanol groups and subsequent surface silylation. The hybrid material was characterized by elemental analyses, IR spectroscopy, X-ray diffraction, and nitrogen sorption, indicating a successful tailoring inside the silicate SBA-15 and the maintenance of the well-ordered mesostructure. This hybrid material is a promising heterogeneous catalyst for the Tishchenko reaction, where it is superior to the homogeneous correspondent in deactivation behavior, reusability and relative tolerance to oxygen, particularly in the control of selectivity of mixed Tishchenko reaction due to the steric hindrance and the diffusion control derived from the surface confinement. [Copyright &y& Elsevier]

Abstract: i-PrOZnEt is an excellent reagent to promote the aldol-Tishchenko reaction of the aliphatic aldehydes tethered with other labile functional groups. The 1,3-diol monoesters 4 were formed as the major products, which could be converted to α-methylene ketones 7 in two steps in good yields. [Copyright &y& Elsevier]

[RuCl(SiMe3)(CO)(PPh3)2] (1) was found to catalyze dimerization of aldehydes RC(O)H yielding esters RC(O)—OCH2R (3) in a Tishchenko type reaction. Aldehydes with α-hydrogen atoms (R = Me, Et, iPr, iBu) reacted quantitatively within 2 days (5 mol% catalyst, 70 °C in C6D6) whereas those without α-hydrogen atoms (R = tBu, Ph) did not react at all. In the case of benzaldehyde (R = Ph), well shaped crystals of [RuCl(O2CPh)(CO)(PPh3)2] (4) precipitated from the reaction mixture. Molecular structures of catalyst 1 and benzoato complex 4 were established by single-crystal X-ray diffraction analyses exhibiting square pyramidal (1) and octahedral (4) complex, respectively. Using 1:1 mixture of acetaldehyde and propanal a crossed esterification reaction took place forming esters RC(O)—OCH2R′ (3, R/R′ = Me/Me, Et/Et; 5, R/R′ = Me/Et, Et/Me). In the case of tBuC(O)H a crossed esterification reaction with RC(O)H (R = Me, Et) took place yielding only two products, namely the symmetrical esters RC(O)—OCH2R (3, R = Me, Et) and the crossed products of the type RC(O)—OCH2tBu (6, R = Me, Et). As shown with propanal, ester formation is completely suppressed by water. Because ruthenium catalyst 1 was prepared by reaction of [RuCl(H)(CO)(PPh3)3] (2) with H2C = CHSiMe3, complex 2 was also used as catalyst in the reaction with aldehydes. It proved to be non-active, but in the presence of H2C=CHSiMe3 (H2C=CHSiMe3:RC(O)H = 1:1) catalytic formation of cyclotrimers of aldehydes (RCHO)3 (7) and aldol condensation products RCH=CR′—C(O)H (8, R = Et, iBu; R′ = R−CH2) was observed. [Copyright &y& Elsevier]

Catalytic behavior of solid bases for mixed Tishchenko reaction in which an equimolar mixture of two different aldehydes is allowed to react was investigated employing the combinations of benzaldehyde and pivalaldehyde, pivalaldehyde and cyclopropanecarbaldehyde, and cyclopropanecarbaldehyde and benzaldehyde. The reactions were performed at 353 K for 4 h in vacuo without solvent using 5 mmol of each aldehyde and 100 mg of solid base catalyst. For all the combinations, the catalytic activity of alkaline earth oxides increased in the order of BaO≪MgO2O3, ZrO2, ZnO, γ-alumina, hydrotalcite, KF/alumina, and KOH/alumina produced either no amount or very small amounts of cross-esterification and self-esterification products. Quantum chemical calculations carried out at the PM3-MO level for the positive charges on the carbonyl carbon atoms of aldehydes and the structure parameters of the active species for the ester formations indicated that the selectivities to four Tishchenko dimers over MgO and CaO are determined primarily in the step of the nucleophilic addition of the active species (PhCH2O-, tBuCH2O-, and C3H5CH2O-) to the carbonyl carbon atoms of aldehydes. The reaction of the aldehyde having more positively charged and sterically less hindered carbonyl carbon atom with the active species having less hindered oxygen atom proceeds faster. We also attempted the application of solid base catalysts to the challenging Tishchenko reaction of furfural, and excellent results were obtained with CaO and SrO. For instance, when furfural (10 mmol) was treated with SrO (100 mg) without solvent at 353 K for 6 h in vacuo, almost quantitative conversion to the corresponding ester was accomplished. Furthermore, application of SrO to the Tishchenko reaction of 3-furaldehyde was carried out successfully. The catalytic systems were also successfully applicable to the intramolecular Tishchenko reaction (lactonization) of o-phthalaldehyde to phthalide. For example, treatment of o-phthalaldehyde (1 mmol) with CaO (50 mg) in benzene (1 mL) solvent at 313 K under N2 produced phthalide quantitatively in a short time of 15 min. We finally refer to the perspective of application of solid base catalysts to Tishchenko reaction. [ABSTRACT FROM AUTHOR]

This review describes the preparation, characterization and application of KNH2 loaded on alumina and KF loaded on alumina. These strong solid bases catalyze a variety of organic reactions in a very selective manner. The reactions include isomerizations of alkenes and alkynes, dimerization of alkynes, Tishchenko reaction, and the reaction of silanes to form of Si–C, Si–N and Si–O bonds. [ABSTRACT FROM AUTHOR]

An optically pure macrolide containing 1,3-dioxolane, gem-dimethylcyclopropyl, and hydrazide fragments was synthesized from (+)-3-carene via [1+1]-condensation of the product from sequential ozonolysis-reduction and Tishchenko disproportionation of (3S,4S)-[(3R,4R)-4-isopropyl-3-methyl-6-oxoheptyl]-4-isopropyl-3-methyl-6-oxoheptanoate with the hydrazide of L-(+)-tartaric acid acetonide. [ABSTRACT FROM AUTHOR]