Palladium-catalyzed hydrosilylation of ynones to access silicon-stereogenic silylenones by stereospecific aromatic interaction-assisted Si-H activation

Catalytic C(sp)–Si cross-coupling silylation of alkynyl bromides with hydrosilanes by palladium catalysis

“…We also found that the steric repulsion of dihydrosilanes played an important role in the C(sp)-Si cross-coupling reaction; for example, the Pd-catalyzed cross-coupling reaction of alkynyl bromide 1a with a hydrosilane bearing a less bulky aryl group resulted in the desired product 3ae in only 25% yield, and two other orthosubstituted arylsilanes bearing a larger bulky aryl group conveniently transformed into alkynylsilanes 3af and 3ag in good yields (88% and 66%, respectively). Similar to previous findings in Si-H bond activation by palladium catalysis, 16 these experimental results showed that steric hindrance might dramatically affect the reactivity of hydrosilanes in this crosscoupling reaction, in which the steric repulsion served as an important factor in the stability of the active silyl palladium species.…”

Cobalt‐Catalyzed Regio‐, Diastereo‐ and Enantioselective Intermolecular Hydrosilylation of 1,3‐Dienes with Prochiral Silanes

“…Our studies commenced with reaction of simple 1,3‐diene 1 a with methylphenylsilane 2 a in the presence of Co complexes derived from various chiral phosphine ligands (Table 1). Unlike previous hydrosilylation of alkenes and alkynes with a limited scope of prochiral silanes, [7r, 8q–s] we expected that high stereoselectivity could be achieved for diversified prochiral silanes without the requirement for installation of a specific substituent. Co complexes generated from bisphosphines 4 a – d could not promote the reaction (entries 1–4).…”

“…Catalytic enantioselective hydrosilylation of unsaturated C−C bonds represents one of the most straightforward and atom‐economical approaches for synthesis of chiral organosilanes. Although metal‐catalyzed protocols for enantioselective hydrosilylation of terminal alkenes, [7b,d–k,m, n] 1,1‐disubstituted alkenes, [7l] 1,3‐dienes, [7s, 12] allenes, [13] cyclopropenes, [7t] vinylcyclopropanes, [7u] gem ‐difluoroalkenes [7v] to furnish a C‐stereogenic center containing a C−Si bond have been revealed (Scheme 1a), more challenging construction of Si‐stereogenic centers through catalytic enantioselective intermolecular hydrosilylation of alkenes and alkynes remained scarce (Scheme 1b) [7r, 8q–s] . Moreover, such processes have significant limitation on the diversity of the prochiral silanes, requiring installation of specific substituents on the silanes.…”

Silicon‐Stereogenic Monohydrosilane: Synthesis and Applications

“…Xu and co‐workers reported a Pd‐catalyzed asymmetric hydrosilylation of ynones with diaryl dihydrosilanes (Scheme 16). [33] Notably, the hydrosilylation occurred selectively on the alkyne rather than the carbonyl group, which provides a facile way to access α‐carbonyl vinylmonosilanes Si‐15 in high yields and excellent ee values. The regioselectivity of the hydrosilylation of alkynes ranged from 2/1 to >20/1, depending on the steric hindrance of the ynones.…”