Tin-Mediated Regioselective Benzylation and Allylation of Polyols: Applicability of a Catalytic Approach Under Solvent-Free Conditions

Abstract

The first catalytic version of the stannylene-mediated benzylation and allylation of polyols is reported. The methodology is based on a simple solvent-free protocol that significantly advances, in terms of both experimental ease and synthetic scope, the applicability of tin-promoted selective protections. The described approach is indeed endowed with a very large number of advantages over routine protocols: use of a low catalytic loading of cheap Bu2SnO, a single-step process with avoided use of solvents, a minimally demanding experimental procedure with reactions performed under air, reduced reaction times, a much simpler work up, a wide target scope, and yields that, in many cases, compare favorably to routine protocols. In addition, the catalytic solvent-free approach extends the scope of stannylene chemistry to unprecedented applications to reducing sugars and in the synthesis of highly benzylated building blocks otherwise accessed through much more demanding procedures. From a conceptual point of view, the described results indicate that solvent-free conditions can assist the development of catalytic approaches otherwise ineffective in solution.