Decarboxylative borylation of vinyl-based cyclic carbonates

The synthesis of allylboronates by copper-catalyzed borylation of allylic carbonates with B2pin2 represents a powerful synthetic method.[1,2]So far, thedecarboxylative borylation involves the loss of CO2 but also the... [ view full abstract ]

The synthesis of allylboronates by copper-catalyzed borylation of allylic carbonates with B₂pin₂ represents a powerful synthetic method.[1,2]

So far, thedecarboxylative borylation involves the loss of CO₂ but also the ORmoiety from the -OCO₂R leaving group. We are now suggesting a new decarboxylative borylation procedure that involves the nuceophilicboryl attack[3] on vinyl-based cyclic carbonates, releasing only CO₂ and keeping the hydroxyl group on the final product, to become more atom economically active, and openinig an non existing pathway towards polifunctionalized allylboronates.

A proposed reaction mechanism could be mediated by borylcopper (I) complexes, formed in situ from CuOMe and B₂pin₂, that coordinate the terminal olefin of vinyl-based cyclic carbonates. Next, the addition of borylcopper(I) across the carbon-carbon double bond might produce the alkylcopper species with the concomitant elimination giving the formal anti-S_N2’ product, and promoting the CO₂ elimination. The formation of the E/Z isomers could be due to the formation of two conformations, either of them allowing an anti parallel arrangement of the copper reagent and the leaving group CO₂ from the vinyl-based cyclic carbonates, releasing only CO₂ and keeping the hydroxyl group on the final product, to become more atom economically active, and openinig an non existing pathway towards polifunctionalized allylboronates.

Since absolute stereocontrol in acyclic and cyclic systems is an important synthetic problem, we extended the methodology to obtain principally or exclusively the E or Z isomers for a representative series of vinyl-based cyclic carbonates.

References

[1] H. Ito, Ch. Kawakami, M. Sawamura, J. Am. Chem. Soc., 2005, 127, 16034

[2] a)H. Ito, S. Ito, Y. Sasaki, K. Matsuura, M. Sawamura, J. Am. Chem. Soc., 2007,129, 14856; b) H. Ito, S. Ito, Y.Sasaki, K. Matsuura, M. Sawamura, PureAppl. Chem. 2008, 80, 1039; c) H. Ito, T. Okura, K.Matsuura, M. Sawamura, Angew. Chem. Int.Ed., 2010, 49, 560.

 [3]  a) Y. Makoto, Bull Chem Soc. Japan, 2011, 84, 984; b) J. Cid, H. Gulyás, J.J. Carbó, E. Fernández, Chem. Soc. Rev.2012, 41, 3558; c) R. D. Dewhurst, E. C. Neeve, H. Braunschweig, T. B.Marder, Chem. Commun., 2015, 51, 9594.