AS part of ou COMlWhg intereat (7-4) in the u88 Of steriCa# v bulky substitvents to control reactant conformatton and, in some cases, reactkn ste “ktry, we initiated a study of certain triilkylsilyl substituents, R, SI-. Such substituents, R, SC, have sufficient steric bulk (5-9) to exert control over reactant con-formation in a manner similar to bulky alkyl substituents (70). Thus, a conformational A value of 2.4-2.6 kcal/md Is reported for the trheWkW spup (8, Q). ...