ChemInform Abstract: Asymmetric Nucleophilic Addition to Vinylphosphonates. Part 2.

Abstract

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A helical structure held together by phosphonate C–H⋯O hydrogen bonds

“…As part of a programme of asymmetric synthesis we have prepared a range of compounds containing core groups 1 and 2 (where R is alkyl, vinyl or alkanoyl) in which the phosphorus atom is chiral. 17,18 In both 1 and 2 where R~vinyl, nucleophilic addition results in diastereoselectivity with predictable chirality induction at the b-position to the phosphorus. Thus addition of various carbon nucleophiles (i-propyl, nbutyl, t-butyl, phenyl or CH 2 LCH as their lithium or Grignard reagents) to 3 gives a variety of asymmetric products, specifically compound 4 in the case of i-propyl carbanion addition.…”

Cyclic tri- and Pentavalent Amidoesters and Diamides with a Stereogenic Phosphorus Atom in Asymmetric Synthesis: Part I: Stoichiometric Reagents

“…The removal of the silyl group by treating the reaction mixture with tetrabutylammonium fluoride gave the nonsilylated adducts 141a-e. No diastereoselectivity was observed in the addition of nbutylcupprate to 139a. However, addition to 139b, with a bulkier trityl nitrogen substituent gave modest diastereoselectivites (Scheme 30) [71].…”

“…Nucleophilic addition of a few carbon nucleophiles to optically pure vinyl posphonates 139a,b (prepared by treatment of diastereomerically pure allyl phosphonates 116a,b with DBU) (Scheme 30) [71] which was found to be accelerated by TMSCl and TMEDA gave a mixture of -silylated and nonsilylated adducts 140a-e and 141a-e which were easily separated by chromatography. The removal of the silyl group by treating the reaction mixture with tetrabutylammonium fluoride gave the nonsilylated adducts 141a-e. No diastereoselectivity was observed in the addition of nbutylcupprate to 139a.…”

Stoichiometric asymmetric processes

“…130 Addition of organocopper reagents to unsaturated chiral phosphonate derivatives gave good to poor levels of diastereoselectivity. 131 Under appropriate circumstances, organolithium and magnesium reagents can also add to chiral acceptors without the aid of copper additives. Diastereoselective Michael addition of MeLi to a vinyl selenide bearing a cyclohexanol auxiliary followed by quenching with an alkyl halide gave >15 : 1 diastereoselectivity.…”