Borylation of saturated heterocycles with several heteroatoms. (Review)

New examples of the borylation of a series of five-and six-membered saturated 1,3-and 1,3,2-heterocycles with the formation of cyclic boric esters are described. The probable mechanism of the reaction is discussed. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 643–654, May, 2006.     

Uncatalyzed, anti-Michael addition of amines to β-nitroacrylates: practical, eco-friendly synthesis of β-nitro-α-amino esters

A variety of primary and secondary amines give the conjugate reaction with β-nitroacrylates, via an anti-Michael addition, without any catalyst and/or solvent, allowing good yields of β-nitro-α-amino esters.     

Bifunctional cinchona alkaloids-catalyzed asymmetric [4+2] cycloaddition reaction of β,γ-unsaturated α-keto esters with oxazolones

A highly enantioselective [4+2] cycloaddition reaction of β,γ-unsaturated α-keto esters with oxazolones was realized with readily available cinchona alkaloids as the catalysts. Using this reaction, a series of highly functionalized δ-lactones with adjacent α-quaternary-β-tertiary stereocenters were obtained in high yields (up to 97%) and with good-to-excellent enantioselectivities (up to 97% ee).     

The effect of the migrating group structure on enantioselectivity in lipase-catalyzed kinetic resolution of 1-phenylethanol

We have studied the effects of the acyl moiety on the enantioselectivity of three lipases: Candida antarctica B, Pseudomonas cepacia and Candida cylindracea, frequently used in kinetic resolutions by acylation or hydrolysis. The size of the acyl group was examined using various enol esters during the transesterification of 1-phenylethanol and the hydrolysis of the corresponding phenylethylesters. C. antarctica-B lipase showed the highest selectivity in the transesterification of 1-phenylethanol with isopropenyl and vinyl acetate, vinyl decanoate, vinyl laurate, (E > 200). The esters 1-phenyl -ethyl-acetate, decanoate and laurate are also hydrolyzed with high selectivities (E > 150) with CAL-B. The results can be correlated to the three-dimensional form of each lipase. The effect of the migrating group on the reactivity and selectivity of the lipases are discussed for both reactions.     

One pot synthesis of unsymmetrical dihydropyridines by green,catalyst free and environmentally benign protocol

Abstract

A facile and ecofriendly synthesis of β-enamino esters is reported by reaction of both aliphatic and aromatic amines with β-keto esters by refluxing in ethanol in absence of any catalyst. Addition of α,β-unsaturated aldehydes to the reaction mixture leads to the formation of unsymmetrical dihydropyridine derivatives which generally are metal free hydrogen sources for asymmetric reduction reactions.     

聚对苯二甲酸乙二醇酯和聚对苯二甲酸丁二醇酯化学扩链反应

综述了用于聚对苯二甲酸乙二醇酯（ＰＥＴ）、聚对苯二甲酸丁二醇酯（ＰＢＴ）化学扩链反应的羧基加成型和羟基加成型扩链剂，以及缩合型扩链反应、羧基加成型扩链反应和羟基加成型扩链反应、羧羟基同时加成型扩链反应。讨论了扩链反应、反应特性和扩链产物的性能，并简要介绍了国内研究概况。参考文献２０篇。     

Solvent-Free Acetylation of Thiols Under Catalysis of MgBr2·OEt2

Solvent-free protection of aromatic and aliphatic thiols with acetic anhydride was performed at room temperature under trace quantities of magnesium bromide ethyl etherate, affording rapid formation of various thiol esters in excellent yields.     

The Calculus of HLB Values of Polyoxyethylene Fatty Acid Esters from Quality Control Data

In this article, we obtained equations that permit us to calculate the hydrophilic-lipophilic balance (HLB) value of polyoxyethylene esters from quality control data of the raw materials (fatty acids and polyethylene glycol) and the finished product (surfactant). These data include the acid value of the fatty acid, the hydroxyl value of the polyethylene glycol, and the hydroxyl value of the surfactant. These calculations permit us, moreover, to know the mean molecular masses of fatty acids, of polyethylene glycol, of monoester and diester, and the proportion of polyoxyethylene monoester and polyoxyethylene diester.     

Stereospecific 1,2‐Migrations of Boronate Complexes Induced by Electrophiles

The stereospecific 1,2‐migration of boronate complexes is one of the most representative reactions in boron chemistry. This process has been used extensively to develop powerful methods for asymmetric synthesis, with applications spanning from pharmaceuticals to natural products. Typically, 1,2‐migration of boronate complexes is driven by displacement of an α‐leaving group, oxidation of an α‐boryl radical, or electrophilic activation of an alkenyl boronate complex. The aim of this article is to summarize the recent advances in the rapidly expanding field of electrophile‐induced stereospecific 1,2‐migration of groups from boron to sp² and sp³ carbon centers. It will be shown that three different conceptual approaches can be utilized to enable the 1,2‐migration of boronate complexes: stereospecific Zweifel‐type reactions, catalytic conjunctive coupling reactions, and transition metal‐free sp²–sp³ couplings. A discussion of the reaction scope, mechanistic insights, and synthetic applications of the work described is also presented.