Sylvie Robin

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)

Microbiological reduction of keto-sulfones. Application in a three-step synthesis of (S)-(+)-β-angelica lactone

Abstract Microbiological reductions of several keto-sulfones led to the corresponding hydroxy-sulfones in moderate to high enantiomeric excess. A three-step synthesis of (S)-(+)-β-angelica lactone from ethyl-4-oxo-3-(phenyl-sulfonyl)-pentanoate via the intermediate chiral alcohol is described.

A convenient asymmetric synthesis of thalidomide

Abstract Benzyloxyamine reacted with BOC-glutamic-α-phenyl ester in the presence of carbodiimide to give BOC-amino-N-benzyloxypiperidinedione. Deprotection of the amino group followed by phthaloylation led to N-benzyloxythalidomide which was then converted into thalidomide.

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.

Preparation of lactones with several ring sizes via the same intermediate

Abstract Several lactones were prepared from (S)-1-(phenylsulfonyl)-3-butanol 2 by cyclization of alkylation products of its silyl derivative 3 with electrophilic reagents bearing a functional group.

Preparation of oxetanes by 4-endo trig electrophilic cyclisations of cinnamic alcohols

Abstract The reaction of substituted cinnamic alcohols with bis( sym -collidine)bromine(I) hexafluorophosphate was examined. In general no oxetane was obtained when a substituent was fixed on the carbonue5f8carbon double bond. However, oxetanes were formed in high yields when two substituents were present in α of the alcohol function.

Bis(sym-collidine)bromine(I) hexafluorophosphate as oxidant

Abstract Primary and secondary alcohols in solution in methylene chloride are oxidised with bis( sym -collidine)bromine(I) hexafluorophosphate in good yields to the carbonyl compounds. For secondary and tertiary alcohols in which one of the substituents is a 4-methoxyphenyl group the oxidation takes place by cleavage of the phenyl- sp 3 carbon bond and formation of bromoanisole and carbonyl compounds.

Halogenation of Pyridinols using Bis(sym-collidine)iodine(I) and Bis(sym-collidine)bromine(I) hexafluorophosphate

Abstract Iodination and bromination of pyridinols was achieved by action of the title reagents in methylene chloride.

A NEW METHOD FOR THE PREPARATION OF THE 6,6 AND 6,7 RING SYSTEMS OF BICYCLIC ETHERS

Abstract Preparation of 2,7-dioxabicyclo[4.4.0]decane and 2,8-dioxabicyclo[5.4.0]undecane derivatives in five steps from dihydropyran are reported. Transformation of 3-bromo-2-allyloxepane into 2,7-dioxabicyclo-[5.4.0]-undecane is also described.

Allylation of oxepane rings

Abstract 2-Allyloxepanes have been prepared reaction of 2-(4-nitrobenzyloxy)oxepanes with allyltrimethylsilane in acetonitrile in the presence of BF3-Et2O or from 2-ethoxyoxepane in liquid sulphur dioxide without catalyst.