The construction of carbon-carbon bonds remains central to organic chemistry. The electroreductive cyclization (ERC) and the electrohydrocyclization (EHC) reactions provide a convenient method for the construction of a sigma bond between two formally electrophilic carbon centers.[1] They occur under mild, metal free conditions and can be achieved using both direct and mediated protocols. Yet, the need to use large quantities of supporting electrolyte can lead to problems during the isolation process and to the formation of significant amounts of waste.[2]

To address these issues, we have explored the use a microflow reactor.  The small distance between the electrodes reduces the ohmic drop, and the large ratio of the electrode surface area-to-solution volume facilitates electron transfer.  As a result, less supporting electrolyte is needed.  Using our apparatus, we have achieved yields comparable to those reported in the literature while significantly reducing the amount of supporting electrolyte.  In addition, recycling provides a convenient way to increase the reaction scale and to optimize yields.

References:

1. Miranda, J. A.; Wade, C. J.; Little, R. D. J. Org. Chem. 2005, 70, 8017-8026.

2. Moëns, L.; Baizer, M. M.; Little, R. D. J. Org. Chem. 1986, 51, 4497-4498.