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A small macrocycle comprising ether‐bridged naphthyl units was prepared in a two‐step synthesis. Single‐crystal X‐ray diffraction of two polymorphs are reported, one of which showed multiple C−H⋅⋅⋅πnaphthyl interactions of a solvent molecule in the cavity of the macrocycle. Chemical reduction led to C−O bond cleavages accompanied by a Z/E isomerization. The resulting twofold negatively charged (E)‐1,2‐bis(2‐naphthyl)ethylene fragment was isolated as its potassium salts. Electronic characterization revealed a singlet ground state, and a marked distortion of the central ethylene unit was observed upon electron uptake. [ABSTRACT FROM AUTHOR]

Lanthanide (Ln) metals are strong reducing agents (E0(Ln3+/Ln0)≈−2.3 V vs. NHE) which can be applied in various manners in organic synthesis. While samarium and ytterbium have been employed for more than 50 years, the last 20 years have seen the emergence of synthetic applications using other metals, such as lanthanum, cerium, praseodymium, neodymium or dysprosium. The large electron reservoir of lanthanide metals, the Lewis acidic character of the Ln3+ ions and their intermediate electronegativity compared to lithium or magnesium can provide unique reactivity patterns. This review provides an overview on the potential of these metals for synthetic organic chemistry in the following areas: 1) for Grignard type reactivity and radical generation, 2) in reduction chemistry involving carbonyl compounds and dehalogenation reactions and 3) in combination with transition metals. [ABSTRACT FROM AUTHOR]

A chemoenzymatic synthesis of the veterinary antibiotic florfenicol is described. The key step involves the dynamic reductive kinetic resolution (DYRKR) of a keto ester by using a ketoreductase‐02 (KRED‐02) to afford the two contiguous stereocenters of the (2S,3R)‐cis‐1,2‐amino alcohol intermediate in >99 % ee and a diastereomeric ratio (dr) of 99 %. This green biocatalysis is environmental friendly with high enantioselectivity and product yields. Two methods for the nucleophilic fluorination step involved the use of aziridines and cyclic sulfates to safely prepare fluoroamines with high regioselectivity. Additional studies have indicated that KRED‐02 can also be used to afford chiral alcohol (S)‐21 in good yields with high enantioselectivity. This study shows that the integration of biocatalysis into organic synthesis can be useful and provide industrial opportunities for applications of florfenicol. [ABSTRACT FROM AUTHOR]

A high‐yielding and high‐rate reduction method that operates with alkenes, alkynes, azides, nitriles, and nitroarenes was developed and optimized. The method makes use of sodium borohydride reduction of CoSO4 under release of hydrogen along with the formation of Co2B as a nanoparticle material. The produced Co2B activates the various functional groups for hydride reduction. The protocol was proven to operate with an assortment of functional groups to provide good to excellent yields. Furthermore, the reduction method was successfully adapted, implemented, and developed for a continuous flow approach using the multi‐jet oscillating disk (MJOD) flow reactor platform at atmospheric pressure. [ABSTRACT FROM AUTHOR]

Catalytic hydroboration and cyanosilylation of a wide range of aldehydes and ketones, with pinacolborane (4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolane) and trimethylsilyl cyanide, respectively, in the presence of titanium(IV) complexes [κ2‐{(C5H4N)CH2N‐P(=Se)Ph2}Ti(NMe2)3] (1) and [{κ2‐(C6H4F)NP(=Se)Ph2}Ti(NMe2)3] (2) are reported. The catalytic hydroboration and cyanosilylation processes are high‐yielding and general, and result in efficient conversion of carbonyl compounds into the corresponding products under mild conditions. Titanium catalyst 1 exhibits high tolerance toward several functional groups. First‐order kinetics with respect to the catalyst and each of the substrates were observed for the titanium‐catalyzed hydroboration of carbonyl compounds. First‐principles calculations were performed to explore the catalytic hydroboration reaction mechanism. In addition, a combination of both reactions and sequential cyanosilylation/hydroboration is reported. TiIV complexes 1 and 2 were prepared by aminolysis of [Ti(NMe2)4] with protic ligands [(C5H4N)CH2NHP(=Se)Ph2] (L1H) and [(C6H4F)NHP(=Se)Ph2] (L2H), respectively. The third titanium complex [κ4‐{Ph2P(=Se)NCH(C5H4N)CH(C5H4N)P(=Se)Ph2}‐Ti(NMe2)2] (3) was obtained from the reaction between [Ti(NMe2)4] and ligand L1H in a 1:2 molar ratio at room temperature. The molecular structures of complexes 1 and 3 in the solid state are reported. [ABSTRACT FROM AUTHOR]

This communication describes a synthetic study of the originally proposed structure of mycalol (1) and the total synthesis of the actual structure of the anticancer marine natural product mycalol (2). The total synthesis of the originally proposed structure of mycalol (1) was targeted by a late-stage asymmetric dihydroxylation, which resulted in an inseparable mixture of diastereomers. Thus a new strategy was developed for the total synthesis of the revised structure of mycalol (2); all the stereocentres except the C-2'-OH were created in an asymmetric fashion by using a Maruoka allylation, a Noyori asymmetric reduction, and an asymmetric alkynylation. [ABSTRACT FROM AUTHOR]

The convenient, metal-free reduction of imines that contain an inexpensive and removable chiral auxiliary allowed for the synthesis of the immediate precursors of chiral active pharmaceutical ingredients (APIs). This protocol was carried out under batch and flow conditions to give the correspoding products in high yields with almost complete stereocontrol. In the presence of trichlorosilane, an inexpensive and nontoxic reducing agent, and an achiral Lewis base such as N,N-dimethylformamide, the formal syntheses of Rivastgmine, calcimimetic NPS R-568, and a Rho kinases inhibitor were successfully accomplished. For the first time, both the diastereoselective imine reduction and the auxiliary removal were efficiently performed in a micro- or mesoreactor under continuous-flow conditions, which paved the way towards the development of a practical process for the syntheses of industrially relevant, biologically active, enantiopure N-alkylamines. [ABSTRACT FROM AUTHOR]

A flexible and efficient synthesis of the potent human topoisomerase inhibitor (5 Z,9 Z)-eicosa-5,9-dienoic acid was explored; the presented method represents a generally applicable approach towards demospongic acids and related natural products. Key steps of the synthesis involve chemoselective hydroboration, Corey-Fuchs alkynylation, Z-selective Lindlar reduction, tetrapropylammonium perruthenate catalyzed direct oxidation of a primary alcohol to the corresponding acid, and Arndt-Eistert homologation. Thus, the total synthesis of (5 Z,9 Z)-eicosa-5,9-dienoic acid was achieved in 10 steps in an overall yield of 20 %. [ABSTRACT FROM AUTHOR]

( tert-Butyl- NNO-azoxy)acetonitrile ( 1) is a useful precursor for a number of nitrogen heterocycles. It was found that it could be obtained in good yield by treatment of the salts of ( tert-butyl- NNO-azoxy)(hydroxyimino)acetonitrile with NH2OTs. It is the first case of one-step reduction of an oxime group to a methylene unit using an aminating agent. A plausible reaction mechanism is proposed. In addition, a new strategy for the tetrazole 1-oxide ring construction was developed. This involves a diazo-group transfer to the active-methylene unit of compound 1, followed by intramolecular coupling of the azoxy and diazo groups. The tetrazole structures were confirmed by X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

Benzopyrazinoisoindigo, a pigment reported 40 years ago, should be a good candidate for n-type semiconductors if the reported structure is correct. Reinvestigation of this molecule revealed that it is actually (4 H,4′ H)-benzopyrazinoisoindigo, which could be considered as the reduced form of benzopyrazinoisoindigo, and hence, it is a good candidate for p-type semiconductors. The route toward the synthesis of this molecule was optimized, and a mechanism was accordingly proposed. A field-effect transistor based on this material showed a hole mobility up to 2.5 × 10-2 cm2 V-1 s-1. [ABSTRACT FROM AUTHOR]

Hydrosilanes are cheap, readily available substrates, yet they do not see as extensive use for simple carbonyl reductions as borohydrides. Hydrosilane reducing agents broadly fall into one of two general categories: either a) they are easy to handle and require expensive and/or hazardous additives, or b) they are difficult and/or dangerous to handle. This work details the discovery of mild and functional group compatible conditions utilizing hydrosilatrane for the selective reduction of aryl aldehydes to benzylic alcohols without unwanted formation of ethers or deoxygenated products. This method offers significant advances in silane reductions as silatrane is an air- and moisture-stable yet relatively reactive reducing agent that can be used in benchtop open air reactions. [ABSTRACT FROM AUTHOR]

We herein report the synthesis of 2-deoxy-2-iodo-glycosylamides, glycosylurea, N-glycosylbenzotriazole, and N-glycosyl imidazole by addition reaction of trimethylsilyl amides, imidazoles, and benzotriazoles to D-glucal in the presence of N-iodosuccinimide and propionitrile at 0 °C. Two diastereomers were isolated - the α-mannose and β- gluco isomers. Reduction and substitution reaction of the iodine at position C-2 led to formation of various 2-deoxy- N-glycosides and 2-hydroxy-β- D-glucopyranosylamide. The newly generated compounds were screened for their inhibitory activity against various enzymes that included Nav1.7 sodium ion voltage-gated channel in HEK293 cells and the results are discussed. [ABSTRACT FROM AUTHOR]

Aliskiren is the first-in-class orally active direct renin inhibitor. It was approved in 2007 for the treatment of hypertension. We have designed a new strategy for the convergent synthesis of aliskiren that involves a catalytic stereoselective nitroaldol reaction as the key step. A new enantiopure nitroalkane (synthon A1), prepared in only three steps from a commercially available enantiopure 2-(arylmethyl)-3-methyl butanol derivative, was successfully used in a copper-catalysed Henry reaction to give a nitrolactone intermediate in which the correct configuration for the final product was established at all four stereocentres. Nitro-group reduction, Boc-protection of the resulting amine, aminolysis of the lactone with 3-amino-2,2-dimethylpropionamide, and finally Boc-deprotection led to the enantiopure renin inhibitor aliskiren. [ABSTRACT FROM AUTHOR]

Described herein is the reaction of electron-rich aromatic compounds with aliphatic carboxylic acids treated with a catalytic amount (5 mol-%) of InI3, 1,1,3,3-tetramethyldisiloxane (TMDS), and molecular iodine. The reductive monoalkylation occurs smoothly to produce the corresponding aryl alkane derivatives. [ABSTRACT FROM AUTHOR]

The amine-bis(phenolate) iron(III)-catalysed reduction of ketones and aldehydes to the corresponding secondary and primary alcohols by a consecutive hydrosilylation/hydrolysis process is reported. The amine-bis(phenolate) iron(III) catalyst is easily accessible, stable towards moisture and air and has a broad substrate scope. [ABSTRACT FROM AUTHOR]

We describe the indium-catalyzed reductive iodination of aliphatic and aromatic esters with iodine and 1,1,3,3-tetramethyldisiloxane (TMDS). This reducing procedure accommodates a variety of esters, including esters containing alkyl groups, halogens, a hydroxy group, a thioether, and an alkene moiety. Also, this procedure was applied to the cleavage of carbon-oxygen bonds in acrylate polymers. [ABSTRACT FROM AUTHOR]

Two rare sugars - 1-deoxy- L-fructose and L-sorbose - were synthesized from inexpensive starting materials by a carbonyl translocation method developed in our laboratory. Reduction of a known starting compound gave a 1,5-diol derivative. Selective protection of the corresponding primary alcohol and oxidation of the secondary alcohol provided the desired product in acyclic, protected form. Subsequent deprotection resulted in the production of 1-deoxy- L-fructose from the known starting material in five steps and in a total yield of 42 %. This approach represents the first report of a chemical synthesis of 1-deoxy- L-fructose. A similar strategy was applied to convert inexpensive D-glucose into L-sorbose, which was prepared in five steps from a known starting material in a total yield of 55 %. The synthetic methods represent a complementary method to biological approaches for the synthesis of vitamin C. [ABSTRACT FROM AUTHOR]

Notwithstanding that the highly selective hydrogenation of α,β-enones to allylic alcohols can be realized by using Noyori's Ru bifunctional system, the selective reduction of the C=C bonds in α,β-enones without touching the C=O bonds still lacks a general, simple, and efficient procedure. Ruthenium-catalyzed conjugate hydrogenation of various α,β-enones to saturated ketones with high selectivity was investigated. The most important feature of this procedure was that hydrogen in situ generated from paraformaldehyde (or formalin) and water was employed as the reductant. [ABSTRACT FROM AUTHOR]

The reaction of tricarbonyl(3-methylpentadienyl)iron(1+) cation ( 7) with stabilized carbon nucleophiles affords 4-methyl-5-substituted cyclohexenones. Reaction of 7 with sodium bis[(+)-2-phenylcyclohexyl]malonate afforded a mixture of diastereomers ( de = 60 %); the diastereomeric allylic alcohols resulting from Luche reduction of this mixture were separable by column chromatography. Issues in diastereoselectivity in approaches to synthons for the A-ring of the tachysterols from these cyclohexenones are reported. [ABSTRACT FROM AUTHOR]

A variety of enantiomerically enriched tetrahydrofuran spirocyclic derivatives have been synthesised by a sequential enantioselective proline-induced stereospecific resolution through aldol reaction of ( E/ Z)-(phenylsulfanyl)cycloalkanecarbaldehydes followed by a ketone reduction, acid-catalysed [1,2]-SPh stereospecific migration, and ring-closure reaction. [ABSTRACT FROM AUTHOR]

A convergent synthesis of carbocyclic sinefungin ( 2), its C-5 epimer 3a, and adenine-modified derivative 3b is described. The key features of our approach include the use of commercially available L-methionine and readily available (1 R,4 S)-4-hydroxy-2-cyclopentenyl acetate as starting materials, a cross-metathesis reaction, an enzymatic kinetic resolution, and a Staudinger reduction. The current synthesis is flexible and, therefore, provides convenient access to the synthesis of various carbocyclic sinefungin analogues for biological evaluation. [ABSTRACT FROM AUTHOR]

The tandem reduction/oxidation of fluorenyl compounds was performed with LiAlH4 under air to afford the corresponding 9-hydroxyfluorenyl derivatives in good yields. This methodology with LiAlH4 is unprecedented and most likely proceeds by an organoaluminium intermediate, and in the proposed mechanism. [ABSTRACT FROM AUTHOR]

The partial reduction of α,β-unsaturated esters and benzoate derivatives to form the corresponding aldehydes was achieved using a flow reactor system within 1 s at a high flow rate (18 mL min-1) under cryogenic conditions (-97 °C). Commercially available diisobutylaluminium hydride (DIBAL-H) was used as the reductant. The desired enals and benzaldehyde derivatives, except for 4-methoxycinnamate and 4-methoxybenzoate, were formed selectively and redox economically in moderate to high yields. [ABSTRACT FROM AUTHOR]

The first stereoselective synthesis of a cis, cis-configured vicinal triamine was achieved, starting from N-cyclohexenylpyrrolidone ( 10). The reaction sequence consists of the stereoselective construction of the trans-configured 1,3-diamide 14, trans-to- cis isomerization via enols or enamines, and subsequent highly stereoselective reduction of the intermediate imine 17D to the amine 18A. The postulated reaction pathway explains the observed stereoconvergence and is supported by calculation of the heats of formation of its intermediates at the PM3 level. LiAlH4 reduction of 18A yielded the tetracyclic aminal 19, which was converted into the pyrrolidinylquinoxaline 7, which showed low to moderate affinity towards κ and σ1 receptors. [ABSTRACT FROM AUTHOR]

Both the efficiency and the stereoselectivity in baker's-yeast-mediated reduction of ketones are strongly influenced by both the presence and the position of sulfur substituents, or indeed by the use of sulfur-containing additives. Interestingly the oxidation level of the sulfur substituent has a powerful impact on the outcome of the yeast reduction. It is apparent that use of the sulfone moiety as a substituent to influence the efficiency and stereoselectivity in ketone reduction is substantially more effective than use of the analogous sulfide and sulfoxide moieties. [ABSTRACT FROM AUTHOR]

The article presents abstracts on topics related to chemistry including baker's yeast reduction of ketones, synthesis of β-sulfinylamino isocyanides, and enantiospecific synthesis and biological activities of a nuphar alkaloids.

A Staudinger/aza-Wittig reaction sequence is described that is catalytic in phosphorus. Towards this end, the phosphane oxide is reduced in situ by diphenylsilane, which allows for substoichiometric amounts of the catalyst 5-phenyldibenzophosphole to be used. The substrate scope is investigated and benzoxazoles, benzodiazepine imidates and a 2-methoxypyrrole were successfully synthesized. These investigations show that a fast aza-Wittig reaction is required to obtain high yields. [ABSTRACT FROM AUTHOR]

Amino-substituted pyrrole-fused perylenebis(dicarboximides) have been prepared from tri- or tetrabromoperylene prcursors by using the classical azidation conditions for the substitution of aromatic halogen, that is, NaN3, sodium ascorbate, CuI, and N, N-dimethylethane-1,2-diamine in DMSO/H2O. The pyrrole-fused dyes are highly photochemically and thermally stable, which may be useful for labelling and as building blocks for the synthesis of functional molecular materials. [ABSTRACT FROM AUTHOR]

Efficient and stereocontrolled synthesis of size-defined hyaluronan oligomers is described for the first time starting from natural chondroitin polymer. Semisynthesis from chondroitin polymer afforded a disaccharide fragment that was used as starting material for the efficient preparation of a protected hyaluronic acid disaccharide building block. Selective inversion of configuration at C-4 of the D-galactosamine in the chondroitin disaccharide was one of the key steps necessary to afford a hyaluronic disaccharide skeleton. Stereoselective glycosylation, efficient reduction of the N-trichloroacteyl group into the corresponding N-acetyl group and deprotection afforded hyaluronan oligomers in good yield. [ABSTRACT FROM AUTHOR]

Copper-catalyzed and highly chemoselective reduction of N-alkynylamides by a boron addition-protonolysis protocol is presented. The reaction proceeds with the addition of boryl-copper complex to N-alkynylamides with high regioselectivity and stereoselectivity, followed by regiocontrolled transmetallation of the α-site of the alkenylboronate with MeOCuL to afford N-alkenylamides in good yields. Deuterium labeling experiments indicated that both of the alkenyl hydrogen atoms originate from the additive methanol. [ABSTRACT FROM AUTHOR]

Iridium-catalyzed direct dehydroxylation of alcohols with hydrazine was developed through a combination of the oxidation of alcohols and the Wolff-Kishner reduction. This protocol is simple to perform and highly efficient for a series of primary, benzylic and allylic alcohols. [ABSTRACT FROM AUTHOR]

Several classes of arylphosphorus acid amides have been tested in reactions with alkali metal solutions in liquid ammonia. The outcomes of such reactions depend on the structures of the starting materials. Generally, two processes - Birch reduction or cleavage of the P-aryl bond - can be operative. Diarylphosphinic amides tend to undergo double Birch reduction to afford bis(cyclohexadienyl)phosphinic amides. [ABSTRACT FROM AUTHOR]

A short and efficient total synthesis of the alkaloid isosolenopsin and its enantiomer has been achieved. The key step was a ω-transaminase-catalysed regioselective monoamination of the diketone pentadecane-2,6-dione, which was obtained in a single step through the application of a Grignard reaction. Initial low conversions in the biotransformation could be overcome by optimisation of the reaction conditions employing suitable cosolvents. In the presence of 20 vol.-% N, N-dimethylformamide (DMF) or n-heptane the best results were obtained by employing two enantiocomplementary ω-transaminases originating from Arthrobacter at 30-40 °C; under these conditions, conversions of more than 99 % and perfect stereocontrol ( ee > 99 %) were achieved. Diastereoselective chemical reduction (H2/Pd/C) of the biocatalytic product gave the target compound. The linear three-step synthesis provided the natural product isosolenopsin in diastereomerically pure form ( ee > 99 %, dr = 99:1) with an overall yield of 64 %. [ABSTRACT FROM AUTHOR]

An unprecedented one-pot tandem reduction of oxo and ene/yne functionalities of substituted isatins is disclosed for the synthesis of oxindole derivatives in excellent yields. The reaction is simply performed by treating N-(2-alkenyl)/propargylisatins with an excess amount of hydrazine hydrate (25%) under catalyst-free refluxing conditions. The reduction process appears to be quite unique and proceeds quite efficiently without the aid of any catalyst at ambient pressure. [ABSTRACT FROM AUTHOR]

"One advice that I give my students is to try and understand reaction mechanism." Find out more about this author's research at https://doi.org/10.1002/ejoc.201801115. "One advice that I give my students is to try and understand reaction mechanism." Find out more about this author's research at https://doi.org/10.1002/ejoc.201801115. [ABSTRACT FROM AUTHOR]