[3 + 2]-Annulation of -Difluoroalkenes and Pyridinium Ylides: Access to Functionalized 2-Fluoroindolizines.

A [3 + 2]-annulation of -difluoroalkenes and pyridinium ylides was developed employing ambient air as the sole oxidant in an open-vessel manner, affording a series of multifunctionalized 2-fluoroindolizines in moderate to good yields. In this reaction, -difluoroalkene acts as a C2 synthon and entirely avoids the competitive addition-elimination process, which provides facile access to 2-fluoroindolizines.