Heteroatom Exchange Chemistry in (Z)-1-R-2-(4 ',4 '-dimethyl)-2 '-oxazolin-2 ' yl)-eth-1-en-1-ols: Access to Chelate-stabilized Thioester Analogues of Dithiooxophosphoranes

The exploration of S- or Se-for-O exchange with (Z)-1-R-2-(4',4'-dimethyl-2'-oxazolin-2'-yl)-eth-1-en-1-ols (1: R = Ph, Me, CF3, Ph-p-OMe) is described. The use of P4S10, intended to facilitate O <-> S exchange, leads to the isolation of rare examples of air-stable thioester analogues of dithiooxophosphoranes. Clean heteroatom exchange can be realized using Lawesson's Reagent in good to moderate yields. Woollins' selenation reagent leads to the isolation of an unusual example of a selenazolidine product (10) in trace amounts.