1-Trimethylsilylpropargylic alcohols

Trimethylsilyloxyailenes a,f -unsaturated ketones.6 1-Trimethylsilylpropargylic alcohols (I) on treatment with a catalytic amount of n-butyllithium in THF undergo Brook rearrangement to give trimethylsilyloxyailenes (2). If 1 equivalent of n-butyllithium is used and hexane is the solvent the intermediate (b) can be alkylated to afford a./i-nnsaluralcd ketones (3) alter acidic work-up. 

Dimethyl acetylenedicarboxylate (DMAD) (125) is a very special alkyne and undergoes interesting cyclotrimerization and co-cyclization reactions of its own using the poorly soluble polymeric palladacyclopentadiene complex (TCPC) 75 and its diazadiene stabilized complex 123 as precursors of Pd(0) catalysts, Cyclotrimerization of DMAD is catalyzed by 123[60], In addition to the hexa-substituted benzene 126, the cyclooctatetraene derivative 127 was obtained by the co-cyclization of trimethylsilylpropargyl alcohol with an excess of DMAD (125)[6l], Co-cyclization is possible with various alkenes. The naphthalene-tetracarboxylate 129 was obtained by the reaction of methoxyallene (128) with an excess of DMAD using the catalyst 123[62],... 

The same selectivity was obtained when starting directly from a y-trimethylsilylpropargyl alcohol in a one-pot reaction [109, 112] (Scheme 7-96). 

Brook rearrangement. a-Trimethylsilylpropargyl alcohols undergo Brook rearrangement to afford allenyl silyl ethers, which can be used to condense with aldehydes. Silyl group transfer from the ether four bonds apart is preferred after the Sn/Li exchange from silyl ethers of l-tributylstannyl-l,3-alkanediols. °... 

Diallenyltin dibromide, prepared by treatment of propargyl bromide with metallic tin in the presence of metallic aluminum in dry tetrahydrofuran, reacts with aldehydes and ketones to afford 3-alkynic alcohols selectively (Scheme 4). This result is different from a previous report in which an a-allenic alcohol was found to be a major product from a propargyltin reagent prepared from a tin(II) halide. " On the other hand, -alkynic and a-allenic alcohols were synthesized selectively by the reaction of aldehydes and ketones with bis(trimethylsilylpropargyl)tin diiodide using different solvent systems (Scheme S). "... 

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