Synthesis and Characterization of Spirosilanes – 1,2‐Hydroboration and 1,1‐Carboboration

Abstract

Starting from dichloro(divinyl)silane, the dialkynyl(divinyl)-silanes (CH 2 =CH) 2 Si(CϵCR) 2 (R = tBu, p-tolyl, 3-thienyl, CH 2 NMe 2 ) were prepared. These silanes were treated with 9-borabicyclo[3.3.1]nonane (9-BBN) for 1,2-hydroboration of the vinyl groups. The hydroboration products rearranged quickly and quantitatively by intramolecular 1,1-carboboration into the respective target compounds, the axially chiral 5-silaspiro[4.4]nona-1,6-dienes bearing boryl groups at the 2-and 7-positions and the R substituents at the 1-and 6-posi-

Hydroboration of alkynylchlorosilanes as an efficient route for the synthesis of SiNNB heterocycles

“…A considerably sharper resonance was observed at a higher field with a chemical shift of δ = 9.3 ppm for compound 1 , revealing that the B atom is four‐coordinated. [ 28,31,32 ] As discussed above, 1 contains a nucleophilic NMe 2 group, which probably interacts with the Lewis‐acidic boron atom to form a donor–acceptor bond. This interaction favors the formation of the E ‐configuration as observed for the resulting alkenyl group (see above).…”

1,1‐Carboboration through Activation of Silicon–Carbon and Tin–Carbon Bonds

“…The reactions have been successful for nearly all the compounds (intermediates and final products) except in the case of the t Bu‐substituted 5‐silaspiro[4.4]nona‐1,6‐diene derivative 20,25. Some representative examples are given in Scheme (for more details see22,27,28).…”

“… Protodeborylated spirocompounds isolated so far. Intermediates bearing allkynyl groups at silicon atoms also undergo protodeborylation 22,27,29…”

Synthesis of 4‐silaspiro[3.4]octa‐1,5‐diene derivatives: hybrid spiro compounds

“…We have reported the spirosilanes 4‐silaspiro[3.3]hepta‐1,5‐dienes ( A ) and 5‐silaspiro[4.4]nona‐1,6‐dienes ( B ) (Fig. ) containing axially chiral silicon atoms.…”

“…) containing axially chiral silicon atoms. The reactions were carried out for a variety of substituents on ring carbons and it was concluded that the nature of R (alkyl, aryl, heteroaryl) does not affect the course of chemical reactions …”