Triphenylsilyl enol ethers

The nucleophilic reactivities of silyl enol ethers (58, R1 = alkyl) and silyl ketene acetals (58, R1 = 0-alkyl) have been measured for the triphenylsilyl (R2 = H5) substrate, and its perfluoro analogue (R2 = F5), using benzhydrylium cations as reference electrophiles.224 The triphenyl compound is 10 times less reactive than its trimethyl equivalent, but the perfluorination causes the C=C nucleophilicity to drop by 3-4 orders of magnitude. The new compounds have been placed on scales of nucleophilicity taken from the literature. 

Triphenylsilyl ethers are similar in lability to TMS ethers toward basic hydrolysis but they are about 400 times more stable than TMS ethers towards acid hydrolysis. A triphenylsilyl ether group played an important strategic role in the finale of a synthesis of the polyether antibiotic Lonomycin A [Scheme 4.96],154 Model studies of the directed aldol reaction by which the lithium enolate 96.1... 

Difluoro enol silyl ethers are formed by the Grignard reaction of trifluoro-methyl triphenylsilyl ketone. ... 

---