Stereoselective Carbon-carbon Bond Forming Reactions Using Chiral Phosphorus(v) Compounds and the Derived Anions

Download or read book Stereoselective Carbon-carbon Bond Forming Reactions Using Chiral Phosphorus(v) Compounds and the Derived Anions written by Jung Ho Kim and published by . This book was released on 1992 with total page 754 pages. Available in PDF, EPUB and Kindle. Book excerpt: C$sb2$-Symmetric diamines were synthesized in order to examine carbon-carbon bond forming reactions using chiral auxiliary-based phosphorus reagents. The general utility of these diamines as chiral auxiliaries in the diastereoselective alkylation of P-alkyl anions was examined. A systematic study of the alkylation of the P-alkyl anions was accomplished varying N-alkyl and P-alkyl substituents. High diastereoselectivity was achieved with N-neopentyl substrates (up to 92:8 diastereoselectivity). The P-allyl anions with varying phosphorus substituents have heen investigated. The diastereoselectivity and the regioselectivity of Michael reactions of chiral cis-oxazaphosphorinanes with cyclic enones were very high. The reaction with chiral trans-oxazaphosphorinanes was not selective. The conjugate addition reaction of a variety of P-allyldiazaphosphorinanes with cyclic enones, varying the substituent of P-allyl unit, was highly regio- and diastereoselective. The nucleophilic addition to the $alpha,beta$-unsaturated phosphorus(V) compounds proved to be highly nucleophile-dependent. The nucleophiles with certain range of pK$sb{rm a}$ values (25-32) have been shown to react with the $alpha,beta$-unsaturated phosphorus(V) compounds. The diastereoselectivity of the reaction with sulfone stabilized anions or the amide enolates was low in either the internal or relative sense due to the flexible conformation of the P-propenyl side chain. The general reactivity of P-acyl enolate was extraordinarily low toward usual electrophiles except for silylating agents (TMSCl, TESCl) which produced (E)-silyl enol ethers exclusively. Asymmetric aldol reaction of the enolates derived from P-acylphosphorus heterocycles were not highly successful (up to 36% e.e.) mostly due to their low reactivity and the nature of the thermodynamically controlled reaction.