Synthesis of Siloles via Rhodium-Catalyzed Cyclization of Alkynes and Diynes with Hexamethyldisilane

Abstract

R h o d i u m -C a t a l y z e d S i l y l a t i v e C y c l i z a t i o n o f A l k y n e s a n d 1 , 6 -D i y n e s

Boron and Silicon-Substituted 1,3-Dienes and Dienophiles and Their Use in Diels-Alder Reactions

“…Matsuda and co-workers reported a synthesis of siloles (151) using a rhodium-catalyzed inter and intramolecular cyclization of alkynes and diynes with hexamethyldisilane (149) (Scheme 40) [37]. This reaction proceeded in 30-70% yields for a number of symmetrical alkynes (148) but yielded intractable mixtures or dienes rather than siloles with unsymmetrical alkynes.…”

Catalytic Synthesis of Heterocycles via the Cleavage of Carbon-Heteroatom Bonds

“…Matsuda reported on the rhodium catalyzed silylative annulation of alkynes with hexamethyldisilane, which afforded fully substituted silole derivatives (Scheme 8a). 23 In this reaction, the use of a rhodium complex ligated by a norborna 2,5 diene improved the yield of the cyclization product. Xi reported on a palladium catalyzed variant of our benzosilole synthesis, in which aryl halide based substrates were used instead of arylboron compounds in an intra (Scheme 8b) 24 and intermolecular (Scheme 8c) 25 annulation with internal alkynes.…”

Construction of Silicon-Containing Seven-Membered Rings by Catalytic [4 + 2 + 1] Cycloaddition through Rhodium Silylenoid

“…The reaction with (pin)B−Si(NEt 2 )-Me 2 (2b) 15 also proceeded efficiently to afford 3a in good yield with the formation of 6b (entry 10). On the contrary, the reaction with Me 3 Si−SiMe 3 , which has been used as a silylene equivalent in the rhodium-catalyzed alkyne−alkyne−silylene [2 + 2 + 1] cycloaddition, 17 did not afford 3a under the conditions identical to entries 9 and 10. It is noted that Pd(dba) 2 with PMePh 2 promoted [4 + 1] cycloaddition (A to I in Scheme 1) rather than [4 + 2 + 1] and [4 + 2] cycloadditions (entries 11 and 12).…”

“…The C−Si bond-forming cyclization accompanied by the cleavage of Si− Me and Si−Ph bonds is reasonably explained by the intramolecular nucleophilic substitution or σ-bond metathesis of F to afford B and M−X (Scheme 1), which has been proposed in the rhodium-catalyzed formation of fivemembered silacarbocycles. 12,17,18 A possible mechanism involving rhodium silylenoid K is proposed (Scheme 5). K is formed through transmetalation between [Rh]−X (J) and borylsilane 2 19 and undergoes regioselective insertion of the C−C triple bond of dienyne 1 into the Rh−Si bond to afford alkenylrhodium L. The intramolecular insertion of the diene moiety of L into the Rh−C bond takes place to form π-allylrhodium M, 20 which affords seven-membered ring 3 or five-membered ring 3′, respectively, through σ-bond metathesis.…”

“…The reaction took place at 80 °C to afford 3a and 3m in 9 and 7% yield, respectively, after 40 h. The formation of Ph–B­(pin) ( 7 , 12%) and Me–B­(pin) ( 8 , 9%) was also confirmed. The C–Si bond-forming cyclization accompanied by the cleavage of Si–Me and Si–Ph bonds is reasonably explained by the intramolecular nucleophilic substitution or σ-bond metathesis of F to afford B and M–X (Scheme ), which has been proposed in the rhodium-catalyzed formation of five-membered silacarbocycles. ,, …”