Allylsilanes have long been recognized as valuable building blocks for organic synthesis. A zinc-catalyzed reaction of cyclopropenes and hydrosilanes provides a convenient route to these versatile unsaturated organosilanes. In this transformation, ZnBr serves as an efficient catalyst, allowing the generation of a zinc vinyl carbenoid intermediate, which is subsequently involved in a Si-H bond insertion. The process shows broad scope, and is amenable to substituted and functionalized cyclopropenes or the functionalization of polysiloxanes. Moreover, zinc-catalyzed carbene insertion into a Ge-H bond is reported for the first time.
Zinc-catalyzed selective cross-coupling of two carbene sources, such as vinyl diazo compounds and enynones, enabled the synthesis of conjugated dienoate derivatives. This reaction involved the unprecedented coupling of a zinc furyl carbene with vinyl diazo compounds through the γ-carbon. Alternatively, dienoates were also prepared by a commutative cross-coupling of zinc vinyl carbenes generated from cyclopropenes and simple diazo compounds.
The synthesis of uncommon bifunctional allylic derivatives bearing a silane and an alcohol within the same allylic framework is reported. This method relies on the coupling of hydrosilanes with substituted and functionalized cyclopropenes, which deliver the allyl fragment. Rhodium(II) catalysts provide regioselective access to vinyl carbene intermediates, which easily undergo Si-H bond insertions. The transformation occurs with complete atom economy and shows a remarkably broad scope, including a intramolecular version for the synthesis of cyclic O-Si-linked compounds as well as the synthesis of the corresponding allyl amines.
A convenient synthesis of cyclopropyl-substituted furan derivatives by a zinc-catalyzed three-component coupling of 1,3-dicarbonylic compounds, 2-alkynals and alkenes is reported. A sequence consisting of an initial Knoevenagel condensation, cyclization, and a final cyclopropanation reaction
A three-component coupling of alk-2-ynals, 1,3-dicarbonyls and silanes is reported. ZnCl2 serves as inexpensive and low-toxic catalyst for the overall transformation, which involves Knoevenagel condensation, cyclization and carbene Si-H bond insertion. The process takes place with atom economy in the absence of organic solvents and shows a broad scope. This reaction proves also applicable to the functionalization of oligomeric siloxanes.
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