Synthesis of Chiral Oxazolo and Thiazolo Isoquinolinones

Significance

2-Alkyloxazolines and 2-alkylthiazo­lines 2, rapidly prepared from natural (S)-amino acids (60-68%), are acylated with 2-halobenzoyl derivatives 1 to afford crude products 3, which undergo stereocontrolled aryl radical cyclization with Bu₃SnH, to form substituted tetrahydro­oxazolo and thiazolo isoquinolin-5-ones analogues 4. Increased stereoselectivity was observed using (Me₃Si)₃SnH as the radical chain carrier reagent. Reasonable scope was established for the conversion which proceeds in modest to good yields.