3- Trimethylsilyl-3-trimethylsilyloxy-l-propene

Preparative Methods allyl trimethylsilyl ether is lithiated with s-butyllithiumin TFIF-FIMPA to give a rapidly equilibrating mixture of a carbanion and a silylallyloxy anion (eq 1). Silylation of the mixture with chlorotrimethylsilane affords 3-trimethylsilyl-3-trimethylsilyloxy-l-propene (1) exclusively. Several other derivatives with bulky substituent(s) on the silyloxy group were also prepared. ... 

Chelation control, as indicated in 5, is also a suitable model for rationalizing the stereochemical outcome of titanium tetrachloride mediated additions of 3,3-dimelhyl-2-trimethylsilyl-oxy-l-butenc (6) or l-methoxy-2-methyl-l-trimethylsilyloxy-l-propene (7) to 3-benzyloxy-2-methylpropanal (4). In both cases, there is almost exclusive formation of the chelate-controlled product (95 5 and >97 3, respectively)13. 

Under catalysis by tris(dimethylaminosulfonium)difluorotrimethylsilicate, 1,5-anhydro-4,6-0-benzylidene-2-deoxy-D-ery//iro-hex-3-ulo-l-enitol reacted with the ketene acetal, l-methoxy-2-methyl-l-(trimethylsilyloxy)-propene, by Michael reaction at C-1 and gave 23. When the catalyst involved was trimethylsilyl triflate the branched derivatives 24 and 25 unexpectedly resulted. These latter products were thought to arise by a trimethylsilyl triflate induced non-selective cleavage of the benzylidene acetal of the initially formed intermediate 23 affording 4-0- and 6-0-benzylic carbenium ions which underwent a subsequent ring closure at C-2. (See Chapter 13 for reaction of the same ketene acetal with glycals). ... 

Dithioacetals derived from alkyl aryl ketones react with the Grignard reagent (1) in the presence of a nickel catalyst. The use of an orthothioester as substrate in place of a thioacetal provides l,3-bis(trimethylsilyl)propenes as a mixture of the ( )- and (Z)-isomers. With a-oxoketene dithioacetals (5), the Grignard reagent (1) reacts, in the presence of copper(I) iodide, to provide l-trimethylsilyloxy-3-thiadienes (eq 9). ... 

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