The addition of hydrogen chloride to olefins is one of the first fundamental reactions discussed in introductory organic chemistry. Yet, this simplest of reactions is rather limited in scope, as addition only occurs at useful rates to strained olefins [1] and to alkenes that lead to stabilized carbocationic intermediates. [2] Consequently, the direct hydrochlorination of monosubstituted and functionally rich alkenes remains unprecedented. Yet, the ability to prepare alkyl chlorides directly from a wide range of alkenes would be highly attractive for the synthesis of complex structures. Our ongoing research program in olefin functionalization has led us to examine the hydrochlorination reaction. Herein, we disclose the conversion of unactivated alkenes to alkyl chlorides under mild conditions [Eq. ( 1)] that is widely tolerant of functionality. Of particular interest is the fact that this unprecedented Co-catalyzed transformation employs para-toluenesulfonyl chloride (TsCl) as Cl source.
Lewis acid or surface-mediated reactions of HCl with simple olefins such as cyclohexene and cycloheptene have been reported. [3] However, these and related approaches are intrinsically limited, because they preclude the use of acidsensitive functional groups common to useful building blocks. [4] A mechanistically distinct palladium-catalyzed process under neutral conditions was recently documented, albeit the addition can only be conducted with styrenes. [5] Moreover, the benzylic chloride adducts were isolable only for electronpoor arenes.
We have reported a series of Co and Mn catalysts that enable the preparation of azides, hydrazine dicarboxylates, and nitriles from olefins. [6][7][8] The ability to carry out other atom-transfer processes would expand and facilitate the synthesis of novel building blocks accessible from alkenes.