(Phosp)hole in one: A palladium‐catalyzed synthesis for directly assembling phosphole skeletons from triarylphosphines through CH and CP bond cleavage was developed. This approach overcomes several of the limitations of the so far reported methods. Phospholes bearing a range of functionalities (including Br, F, CO2Me, Ac, and CN) and an array of fused rings (naphthalenes, anthracenes, furans, and pyrroles) can be easily synthesized.
A rhodium-catalyzed coupling reaction of 2-trimethylsilylphenylboronic acid with internal alkynes is developed for the synthesis of 2,3-disubstituted benzosilole derivatives. A range of functional groups, encompassing ketones, esters, amines, aryl bromides, and heteroarenes, are compatible, which provides rapid access to diverse benzosiloles. Sequential 2-fold coupling enables modular synthesis of asymmetrically substituted 1,5-dihydro-1,5-disila-s-indacene, a π-extended molecule of interest in organic electronics. In terms of the mechanism, the reaction involves cleavage of a C(alkyl)-Si bond in a trialkylsilyl group, which normally requires extremely harsh conditions for activation. Mechanistic studies, including effects of substituents, reveal that C-Si bond cleavage does not proceed through a hypercoordinated silicon species, but rather through a rhodium-mediated activation process. The potential use of the reaction in catalytic asymmetric synthesis of Si-chiral benzosiloles is also demonstrated.
The palladium-catalyzed synthesis of dibenzofused six-membered phosphacycles via carbon-phosphorus bond cleavage is developed. This method is compatible with a range of functional groups, such as esters, amides, and carbamates, which is in sharp contrast to the limitations of the classical method using organolithium reagents.
Pd(ii)-catalyzed synthesis of dibenzothiophene derivatives has been developed. The reaction proceeds through the cleavage of carbon–hydrogen and carbon–sulfur bonds.
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