Synthesis and Anomalous Reactivity of 5-Bromo-3,5- Di-t-Butyl-2-Phenyl-1,2-Oxaphosphol-3-Ene 2-Oxide and its 4-Bromo Analog

Abstract Reaction of 2,2,6,6-tetramethyl-4-heptyn-3-0l with dichlorophenylphosphine leads to 2,2,6,6-tetramethyl-3,4-heptadien-3-1 phenyl phosphinic acid (11, which undergoes Ag+-catalyzed cyclization to 3,5-di-t-butyl-2-phenyl-1,2-oxaphosphol-3-ene 2-oxide (2H, 75-55% z, 25–45% E). Electrophilic bromination of 1 affords 2Br, the 4-bromo derivative of 2H, as a 75% Z, 25% E diastereomer mixture from which pure (Z)-2Br can be isolated.