Room-Temperature Synthesis of Trisubstituted Allenylsilanes via Regioselective C–H Functionalization

Abstract

A Rh(III)-catalyzed o-C-H bond functionalization-based allenylation reaction of allenylsilanes 2 with N-methoxybenzamides 1 affords poly-substituted allenylsilanes with a wide range of attractive functional groups in moderate to excellent yields under very mild conditions (20 °C, compatible with ambient air and moisture). Those products may be transformed to different products with attractive structural features. Careful mechanistic studies suggest the reaction proceeds via o-rhodation, regioselective insertion, and β-H elimination.

Highly Regioselective Radical Amination of Allenes: Direct Synthesis of Allenamides and Tetrasubstituted Alkenes

“…[10] An umber of efficient transformations based on allenes have been successfully realized, [9] however, mild and regioselective radical reactions of allenes are far less developed. [11] More recently,werealized ageneral radical cascade reaction of an alkyne with N-fluoroarylsulfonimide and an alcohol, during which akey nitrogen radical addition to the alkyne,for the formation of vinyl radical intermediate,w as involved.…”

“…strates 1m and 1n,and results showed that 1n,having amore bulky substituent, is more efficient. [10] Thec yclopentyl substrate 1o and naphthyl-substituted allene 1p are also effective.I ti sw orthy to note that the synthetically more attractive silyl motif,w hich is sensitive to oxidants and fluorides,a lso survived the reaction conditions and the desired amination products 2q, 2r,a nd 2s were afforded in 50-67 %y ields.T he more challenging substrate 1t,b earing as trongly coordinating pyridine moiety, [15] also worked well and delivered 2t in 55 %y ield. Remarkably,t he unsymmetrical 1,3-disubstituted allenes were found to be suitable for the amination reaction and delivered the corresponding allenamides 2u-w in acceptable yields,with the nitrogen atom being attached to the less sterically hindered terminal allenic carbon atom.…”

Rh(III)- and Ir(III)-Catalyzed C–C Bond Cross Couplings from C–H Bonds

“…Noteworthy, the stereoselective version of this transformation was developed by Cramer benefiting from a chiral [CpRh]-derived catalysts [96]. Pursuing his experimental work, Ma discovered also that the steric effect of the allene's substituent may drastically influence the outcome of this transformation [97]. Introduction of strongly sterically demanding substituents, like a trialkylsilyl group, prevents formation of the previously observed protonolysis product, and β-H elimination occurs preferentially, hence affording the extra-substituted allene product (Scheme 6c).…”

Synthesis of Isoquinolinones via Regioselective Palladium-Catalyzed C–H Activation/Annulation

“…In contrast, transition-metal catalyzed oxidative C-H coupling reactions between arene and allene remain relatively unexplored, although allenes have been widely applied in transitionmetal catalyzed reactions [51][52][53][54]. The initial effort in this area, reported by Ma [55], resulted in a direct allenylation reaction with N-methoxybenzamide. In 2012, Glorius and co-workers [56] reported the synthesis of hydroisoquinolinones from the first carbometalation reaction of allenes; however, the applicable substrates were limited to alkyl substituted allenes (Scheme 1a).…”