Scalable Birch reduction with lithium and ethylenediamine in tetrahydrofuran

The Birch reduction dearomatizes arenes into 1,4-cyclohexadienes. Despite substantial efforts devoted to avoiding ammonia and cryogenic conditions, the traditional, cumbersome, and dangerous procedure remains the standard. The Benkeser reduction with lithium in ethylenediamine converts arenes to a mixture of cyclohexenes and cyclohexanes; this is operationally easier than the Birch reduction but does not afford 1,4-cyclohexadienes. Here, we report a Birch reduction promoted by lithium and ethylenediamine (or analogs) in tetrahydrofuran at ambient temperature. Our method is easy to set up, inexpensive, scalable, rapid, accessible to any chemical laboratory, and capable of reducing both electron-rich and electron-deficient substrates. Our protocol is also compatible with organocuprate chemistry for further functionalization.

Automated summary

This article presents a Birch reduction method that is simpler, safer, more efficient, and more environmentally friendly, for converting arenes into 1,4-cyclohexadienes. The method is easy to operate, cost-effective, and applicable to various chemical laboratories, making it a new technology with wide application prospects.