An expedient synthesis of cyanoformates via DAST-mediated C C bond cleavage of α-oximino-β-ketoesters

Synthesis of Carbamoyl Fluorides via a Selective Fluorinative Beckmann Fragmentation

“…Herein, we propose a new, cost-efficient, and reliable synthetic route to provide carbamoyl fluorides from α-oximinoamides 3 . We recently demonstrated the concept of fluorinative C–C bond cleavage of activated ketones; the key to this operation was the use of DAST, which plays a dual role as an oxime activator and nucleophilic fluoride donor. , We thus hypothesized that the fluorinative C–C bond cleavage of activated amides 3 enables the synthesis of carbamoyl fluorides 4 (Scheme b). However, the decreased electrophilicity of amides compared to ketones was a concern in this transformation; there were no existing reports of a reaction between tertiary amides and DAST derivatives.…”

Recent Advances in the Synthesis and Transformation of Carbamoyl Fluorides, Fluoroformates, and Their Analogues

“…Later, Lim et al developed a protocol for the synthesis of cyanoformates from β-ketoesters via α-oximino-β-ketoester intermediates, in which acyl fluorides were formed as the other products. [72] (Diethylamino)sulfur trifluoride (DAST) was used as a dualrole reagent to activate the oxime moiety of the key intermediate and to donate a fluoride. When dibenzyl 2-(hydroxyimino)malonate (232) was employed to react with DAST under the standard conditions, a mixture of fluoroformate (233) and cyanoformate (234) was obtained (Scheme 41b).…”

“…The α-oxime group in this malonate might increase the electrophilicity of the ester functionality, leading to the reaction of ester group with DAST. [72] Ramsden et al accomplished the formation of aryl fluoroformates (236) by treatment of trimethylsilyl benzoates (235) with xenon difluoride (XeF 2 ) in CH 2 Cl 2 or C 6 F 6 via an ester rearrangement (Scheme 42). [73] The reaction was solventdependent.…”

A Strategic Synthesis of Fluoroethers via Ring-Opening Fluorinative Beckmann Fragmentation

“…To develop a protocol, we mapped out an unconventional S N 1-type approach based on our previous work; recently, our group reported several fluorinative Beckmann fragmentations (BKF) for the synthesis of acylation reagents III in which the fluoride nucleophile was incorporated into sp 2 carbon centers. The key to the working hypothesis was the recognition of the oxime functionality as a leaving group in α-oximated carbonyl substrates I (Scheme b) . Inspired by recently developed fluorinative ring opening strategies, we postulated that the fluorinative BKF could be adapted to cyclic α-aryloxy oximes such as coumaranone oximes IV .…”