The synthesis of ketones viaα-silyl sulphides

Abstract

α-Phenylthiosilanes (2) have been prepared by alkylation of the anion (4) derived from the 1-phenylthio- 1-trimethylsilylalkane (1). These anions (4) have been prepared by a variety of methods including, direct deprotonation of (1), displacement of a phenylthio group by lithium naphthalenide, addition of an alkyl- lithium to 1-phenylthio-1-trimethylsilylethene (7), and transmetallation of a tributylstannyl moiety. The formation of an alkyl-lithium by reaction of lithium naphthalenide with a phenyl sulphide provided an additional route to (2) from bis(phenylthio)acetals (8). An alternative path to the α-phenylthiosilanes (2) was to reduce the corresponding α-phenylsulphonylsilane (15); these, in turn, being readily available from alkylation or silylation of α-sulphonyl anions. The α-phenylthiosilanes (2) were converted into the O-trimethylsilylphenylthioacetal (18) by the sila-Pummerer rearrangement, although this was complicated by vinyl sulphide (20) formation in certain cases. Subsequent hydrolysis of (18) and (20) gave the ketone (3).