Taming highly unstable radical anions and 1,4-organodilithiums by flow microreactors: controlled reductive dimerization of styrenes

Reduction of styrenes with lithium arenide in a flow microreactor leads to the instantaneous generation of the radical anion of styrenes and subsequent dimerization by fast mixing to yield the corresponding 1,4-dilithium species. The efficiency and selectivity of this reductive dimerization are low in a batch reactor. A series of styrenes undergo the dimerization and the resulting 1,4-dilithium species are trapped with various electrophiles. Trapping with divalent electrophiles such as dichlorosilanes affords precursors for useful yet less accessible cyclic structures such as siloles. Single electron reduction of unsaturated compounds in flow microreactors has thus proved to be a powerful protocol in organic synthesis.