Thermal Rearrangement of Sulfamoyl Azides: Reactivity and Mechanistic Study

Abstract

The rearrangement of sulfamoyl azides under thermal conditions to form a C-C bond while breaking two C-N bonds is reported. Mechanistic study shows that this reaction goes through a Curtius-type rearrangement to form a 1,1-diazene, then which rearranges possibly through both a concerted rearrangement process and a stepwise radical process. This rearrangement could be used in the synthesis of complex biologically active molecules, such as sterols, and piperine derivatives.

N‐Atom Deletion in Nitrogen Heterocycles

“…These observations are consistent with the results from Levin et al [15] . and with our previous report, [13] in which the C−C bond‐forming mechanism was shown to involve a barrierless intramolecular radical coupling reaction. Due to the ring tension in the four‐membered ring, the unexpected 4‐phenylstyrene 26 b′ was achieved with a four‐membered ring arylcyclobutane 26 b as a minor product in the reaction of the five‐membered N‐heterocycle 26 a (Scheme 4 D).…”

“…For N‐heterocycles used in this reaction, one N‐substituent must be benzhydryl, or both N‐substituents must bear stabilizing elements such as benzyl, allyl or be positioned α to a carbonyl group. Inspired by our previous work, [13, 16] herein we report a N‐atom deletion of N‐heterocycles via a sequence of N ‐sulfonylazidonation, Curtius‐type rearrangement and subsequent rearrangement of the 1,2‐diazene intermediate, providing a unique opportunity to promote ring contraction [17] of N‐heterocycles (Scheme 1 F).…”

“…In 2017, we found that sulfamoyl azides derived from linear alkylamines could undergo a Curtius‐type rearrangement to generate a new C−C bond while simultaneously breaking two C−N bonds via the rearrangement of a 1,2‐diazene intermediate (Scheme 1 D). [13] Because N‐heterocycles are ubiquitous structural motifs [9] and can be easily produced by versatile methods, [14] we questioned whether it is possible to provide a general skeletal editing strategy to transform ( n +1)‐membered N‐heterocycles to n‐membered cycles. Given the large number of organic molecules with cyclic structures, this transformation would be extremely useful.…”

“…Based on previous studies, [11, 13, 28] a mechanism is proposed in Scheme 1 F. Nucleophilic substitution by N 3 SO 2 N 3 of a cyclic amine forms a sulfamoyl azide, which undergoes a Curtius‐type rearrangement to generate a 1,1‐diazene intermediate.…”

Stereoselective Synthesis of Cyclobutanes by Contraction of Pyrrolidines

“…Another nitrogen-deletion protocol of secondary amines featuring a Curtius-type rearrangement/nitrogen extrusion was reported by Lu’s group very recently. 27 , 28 Electrophilic nitrogen transfer using in situ generated iodonitrene has been an emerging research area 29 − 34 ( Figure 1 C).…”