A trityl-cation-initiated annulation of benzyl-substituted vinylcyclopropanes (VCPs) with hydrosilanes is reported. Two Si-C(sp3) bonds and one C(sp2)-C(sp3) bond are formed in this process where an intramolecular 6-endo-tet Friedel-Crafts alkylation of...

A hydrosilylation of vinylcyclopropanes (VCPs) catalyzed by the strong boron Lewis acid B­(C6F5)3 is reported. For the majority of VCPs, little or no ring opening of the cyclopropyl unit is observed. Conversely, for VCPs with bulky R groups, such as ortho-substituted aryl rings or branched alkyl residues, ring opening is the exclusive reaction pathway. This finding is explained by the thwarted hydride delivery to a sterically shielded, β-silicon-stabilized cyclopropylcarbinyl cation intermediate.

Catalytic silicon‐carbon or silicon‐heteroatom bond‐forming hydrosilylation has become increasingly important in synthetic chemistry, catalysis and organosilicon chemistry. Herein we report a platinum‐catalyzed one‐pot and tandem hydrosilylation/cyclization of OH‐containing alkynes with dihydrosilanes, allowing for facile synthesis of six‐membered organosilicon compounds, including silyloxycycles and cyclic siloxanes in high yields and with good stereoselectivities.magnified image

A formal (4 + 1)-cycloaddition of vinylcyclopropanes and Et 2 SiH 2 to afford 3,4-disubstituted silolanes is reported. The reaction sequence commences with the known B(C 6 F 5 ) 3catalyzed alkene hydrosilylation with dihydrosilanes. Cleavage of the remaining Si−H bond in the hydrosilylation product assisted by B(C 6 F 5 ) 3 leads to formation of a cyclopropane-stabilized silylium ion. The activated cyclopropane ring is then opened by the in situ-generated borohydride accompanied by ring closure to the silolane. The diastereoselectivity is rationalized by a mechanistic model.

Pd-catalyzed AAA of 1,2-bifunctional nucleophiles and one-pot tandem allylic cyclization/reduction gave corresponding heterocycle products with promising enantioselectivity in good yields.