Intramolecular nucleophilic substitution by phosphinate and thiophosphinate anions: relative rates of formation of five- and six-membered rings

Abstract

In CH₂Cl₂ solution the phosphinate anion BrCH₂CH₂(CH₂)_nCH₂(Ph)P(O)O^– cyclises only 4,3 times faster when n= 0 (five-membered ring product) than when n= 1; for the thiophosphinate anion ClCH₂CH₂(CH₂)_nCH₂(Ph)P(S)O^– cyclisation (via sulfur) is still only 30 times faster when n= 0 than when n= 1.