Difluoroacetaldehyde N‐Triftosylhydrazone (DFHZ‐Tfs) as a Bench‐Stable Crystalline Diazo Surrogate for Diazoacetaldehyde and Difluorodiazoethane

Abstract Despite the growing importance of volatile functionalized diazoalkanes in organic synthesis, their safe generation and utilization remain a formidable challenge because of their difficult handling along with storage and security issues. In this study, we developed a bench‐stable difluoroacetaldehyde N ‐triftosylhydrazone (DFHZ‐Tfs) as an operationally safe diazo surrogate that can release in situ two low‐molecular‐weight diazoalkanes, diazoacetaldehyde (CHOCHN 2 ) or difluorodiazoethane (CF 2 HCHN 2 ), in a controlled fashion under specific conditions. DFHZ‐Tfs has been successfully employed in the Fe‐catalyzed cyclopropanation and Doyle–Kirmse reactions, thus highlighting the synthetic utility of DFHZ‐Tfs in the efficient construction of molecule frameworks containing CHO or CF 2 H groups. Moreover, the reaction mechanism for the generation of CHOCHN 2 from CF 2 HCHN 2 was elucidated by density functional theory (DFT) calculations.