The reaction of 1-allyl-2-vinyl-1H-pyrroles and 1-allyl-2-vinyl-1H-indoles with arylsilanes in the presence of catalytic [Cp(TMS)(2)Y(&mgr;-Me)](2) leads to highly selective cyclization/silylation events. In this process the active catalyst for the reaction, "Cp(TMS)(2)YH", undergoes initial olefin insertion at the vinyl group. Even isopropenyl substituents on the heteroaromatics react in preference to less sterically encumbered allyl groups. Furthermore, the observed regioselectivity reflects an "aryl-directed" process, whereby the more highly substituted secondary or tertiary organometallic is initially generated. This intermediate undergoes cyclization onto the remaining alkene and subsequent silylation by a sigma-bond metathesis reaction, affording the observed products.
COMMUNICATIONSing stages, any diastereoisomer contamination of 6 a or 6b would be apparent from an examination of the camphanate methyl resonances in the 'H NMR spectra. At no stage was any such contamination seen. A two-step deprotection strategy involving removal of the benzyl protecting groups on phosphates by hydrogenolysis and then cleavage of camphanate esters in a concentrated solution of ammonia at 60 "C was effective with no migration of phosphate groups." 'I Tetrakis(ph0sphate)s 2 a and 2b could then be isolated on a gram scale as the cyclohexyl-ammoniumr7a1 or potassium[7d1 salts in overall yields of 60-70% from 4 a and 4 b. The structures of 2 a and 2 b were confirmed by 'H, 13C, and 31P NMR spectroscopy as well as high-resolution
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