G. Rousseau

Enzymatic resolution of racemic lactones

Abstract PPL, HLE or PLE enzymatic resolution of racemic γ, δ and e-lactones gives optically active lactones (ee: 60 to 90%).

Formation of Four-Membered Heterocycles through Electrophilic Heteroatom Cyclization

This review demonstrates the feasibility of the formation of cyclobutane heterocycles through 4-endo and 4-exo electrophile-induced processes. Cyclizations are usually observed upon treatment of linear substrates with electrophiles such as halogens (chlorine, bromine, iodine), haloreagents {NBS, [bis(collidine)X+]Y−, ...}, and more rarely with seleno reagents and metallic salts. Results show that the formation of β-lactones, oxetanes, and β-lactams can be viewed as a general process useful for synthetic purposes. Formation of azetidines and thietanes appears more limited and has been reported in only a few cases. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Improved synthesis of β,X-unsaturated ketones by the reaction of allylic zinc bromides with nitriles.

Abstract The reaction of allylic bromides with nitriles in the presence of ZnAg couple leads, after hydrolysis, to β,X-unsaturated ketones in high yield.

Reaction of ketenealkylsilylacetals with ethyl propiolate

Abstract The reaction of ketenealkylsilylacetals with ethyl propiolate in the presence of different Lewis acids is reported to give Michael-type additions or a [2+2] cycloaddition.

On the Ketene Alkylsilyl Acetal Preparations

Abstract The action of zinc powder with α-bromoesters in the presence of trimethylsilylchloride and TMEDA-Et3N led mainly to E-ketenealkyl-silylacetals while the reaction of trialkylsilanes on alkyl acrylates catalyzed by Wilkinson reagent gave stereoselectively the Z isomers.

Halodecarboxylation of α,β-acetylenic and α,β-ethylenic acids

Abstract Reaction of bis(collidine)iodine(I) (or bromine (I)) hexafluorophosphate with acetylenic acids led to the corresponding iodo(or bromo)acetylenes in high yields. This halodecarboxylation reaction was also observed with acrylic acids substituted in position 3 by an aryl group or an heteroatom.

Preparation of Azetidines by 4-endo trig Cyclizations ofN-Cinnamyl Tosylamides

Formation of azetidines by electrophilic cyclizations have been reported, starting with homoallylic amines (4-exo mode cyclizations). We reported that the formation of these compounds can be carried out starting with allylic amines (4-endo mode cyclizations) using bis(collidine)bromonium(I) hexafluorophosphate as an electrophile. These cyclizations occur via a carbocation intermediate.

Enantioselective hydrolysis of racemic diesters by porcine pancreatic lipase

Porcine pancreatic lipase catalysed hydrolysis of dimethyl succinates, aspartates, and glutamate provides (R) and (S) methyl esters enantioselectively.

Enzymatic resolution of N-Hydroxymethyl γ-Butyrolactams. An access to optically active γ-Butyrolactams

Abstract Enymatic resolution of substituted pyrolidinones was achieved using lipases transesterification of their 1-hydroxymethyl derivatives of vinyl acetate.

Selectivity in the transesterification of esters by supported enzymes

Abstract The regio and enantioselectivities of the transesterification of racemic dimethyl esters by supported enzymes in absence of solvent are studied: preparations of chiral succinates and N-acetyl aminoesters are reported.