Unique zeolite-catalyzed synthesis of nitroketene S,N-acetals

Dimethyl carbonimidodithioates (4a-g, 7a-c) derived from various primary amines and amino acid esters [glycine, (L)-alanine and (L)-phenylalanine] have been condensed with nitromethane in the presence of the rare-earth exchanged zeolite RE(70%)Na Y to give the S,N-acetals (5a-g, 8a-c). Mercuric chloride catalyzed hydrolysis of these (8a-c) has led to the nitroacetyl derivatives (9a-c). The glycine derivative (7a) gives a dimeric product (11) when heated alone with the zeolite

Is the nitro group attracted towards sulphur?

Evidence is presented for a significant, orientation sensitive, attractive intramolecular interaction between sulphur and a nitro group

Zeolites in organic syntheses: a novel route to functionalised ketene S,N-acetals

Active methylene compounds react with bis(methylthio)alkaneimines in the presence of a zeolite catalyst to give functionalised ketene S,N-acetals in good yields

A novel method for resolution of amlodipine

The present invention relates to an industrially feasible and cost-efficient process for the preparation of isomerically pure S-amlodipine besylate hemipentahydrate (1), a useful calcium antagonist inhibitor. Previous workers reported that R-amlodipine-tartrate was crystallized out preferentially from the reaction mixture when naturally occurring L-tartaric acid and racemic amlodipine base in DMSO are mixed. In order to crystallize S-amlodipine-tartrate, the use of unnatural D-tartaric acid as a resolving agent in DMSO was required. However, the cost of D-tartaric acid was not conducive to overall cost efficiency in the resolution protocol. Subsequent to the above observations, we have developed a novel resolving system in which amlodipine base with natural L-tartaric acid in DMF as a solvent gave preferentially the S-form of amlodipine tartrate directly from the reaction. The optimization of this approach by adjusting the water percentage in DMF ensured consistent purity of S-amlodipine (+99%) and satisfactory resolution efficiency