Intramolecular nucleophilic acyl substitution reactions of halo-substituted esters and lactones. New applications of organosamarium reagents
作者:Gary A. Molander、Jeffrey A. McKie
DOI:10.1021/jo00077a053
日期:1993.12
Intramolecular nucleophilic acyl substitution reactions involving a broad range of halo substituted carboxylic acid derivatives have been accomplished in excellent yield employing samarium(II) iodide as the reductive coupling agent. Although particular substrates cyclized most effectively in THF in the presence of tripiperidinophosphine oxide, carboxylic acid esters, the focus of this report, cyclize equally well without such an additive in the presence of a catalytic quantity of iron(III) complexes. Thus a comprehensive series of halo substituted esters were cyclized in excellent yield to the corresponding 4-, 5-, and 6-membered carbocycles. The reaction is extremely mild and selective as demonstrated by experiments wherein alkyl chlorides, acetals, and olefins remain completely intact under the reaction conditions. In addition to introducing a convenient procedure for preparing stereodefined spirocyclic systems, a new ring expansion sequence has been developed that appears extremely general for the preparation of various ring systems.
Cathodic Cyclisation of N-(Oxoalkyl)pyridinium Salts − Formation of Tricyclic Indolizidine and Quinolizidine Derivatives in Aqueous Medium
作者:Jens Heimann、Hans J. Schäfer、Roland Fröhlich、Birgit Wibbeling
DOI:10.1002/ejoc.200300180
日期:2003.8
The cathodiccyclisation of N-(oxoalkyl)pyridiniumsalts, derived from 4-methylpyridine and cyclic ketones, afforded functionalised tricyclicindolizidine and quinolizidinederivatives in high yields. Through systematic variation of the ring size of the ketone and the cyclised ring, a series of four cyclopenta-/cyclohexa[a]indolizidines and -quinolizidines was obtained. The cyclisation was also applied