Bifunctional Skipped Dienes through Cu/Pd-Catalyzed Allylboration of Alkynes with B₂pin₂ and Vinyl Epoxides

Abstract

A method for the use of vinyl epoxides in catalytic allylboration of alkynes is described. This transformation allows for the synthesis of bifunctional skipped dienes bearing both an allylic alcohol and an alkenylboronate from simple starting materials with high regio-and stereoselectivity. These two functionalities provide these products with highly versatile reactivity, as shown by their stereocontrolled conversion into cyclic boron compounds and polyenes.

Catalytic Alkyne Allylboration: A Quest for Selectivity

“…Synergistic Cu/Pd-catalyzed alkyne allylboration was extended to the use of vinyl epoxides by our group ( Scheme 10 ). 24 Substitution reactions with this type of substrate entail an important challenge in terms of control over the regioselectivity (1,2- vs 1,4-addition) and the stereoselectivity of the resulting allylic alcohol. The catalytic system comprising CuCl/PCy 3 and Pd(dba) 2 /dppf proved to be efficient for the three-component coupling between alkynes, B 2 pin 2 , and vinyl epoxides and provided bifunctional skipped dienes as single 1,4-addition products featuring a ( Z )-alkenyl boronate and an ( E )-allylic alcohol.…”

Switching Selectivity in Borylative Allyl–Allyl Cross-Coupling through Synergistic Catalysis

“…Cooperative catalysis offers alternative opportunities compared to single catalyst systems due to the possibility of tailoring each catalytic cycle to achieve selective and divergent product outcomes. , On the basis of our studies on the Cu/Pd-catalyzed allylboration of alkynes, and inspired by the work of Echavarren and Morken on the Pd-catalyzed coupling of allylic electrophiles with allyl-metal reagents, we envisioned that the merge of Cu and Pd catalysis could serve as an efficient platform to achieve the desired selectivity switch in the borylative allyl–allyl cross-coupling. In our mechanistic hypothesis, the allyl copper species catalytically generated from the borylcupration of the allene would undergo a transmetalation with the allyl-Pd(II) complex generated by oxidative addition of an allyl carbonate into a Pd(0) catalyst.…”

Divergent 1,2-carboallylation of terminal alkynes enabled by metallaphotoredox catalysis with switchable triplet energy transfer

“…Transition metal-catalyzed 1,2-carboallylation of alkynes, in which an allyl moiety and another carbon-centered functionality are spontaneously incorporated in one pot, represents a practical tactic for synthesizing substituted 1,4-dienes. 6,7 Despite attractive, only a few examples of 1,2-carboallylation of alkynes, which generally proceed through a two-electron redox process, i.e. , carbo-metalation of alkynes followed by cross-couplings, have been successfully developed via nickel catalysis (Fig.…”