Synthesis of Five-Membered Cyclic Guanidines via Cascade [3 + 2] Cycloaddition of α-Haloamides with Organo-cyanamides

Abstract

The convenient preparation of N2-unprotected five-membered cyclic guanidines was achieved through a cascade [3 + 2] cycloaddition between organo-cyanamides and α-haloamides under mild conditions in good to excellent yields (up to 99%). The corresponding cyclic guanidines could be easily transformed into hydantoins via hydrolysis.

Visible Light-Enhanced [3 + 2] Cycloaddition of N,N-Disubstituted Hydrazines with Organo-Cyanamides: Access to Polysubstituted 1,2,4-Triazol-3-amines

“…17 N-Tosyl-N-aryl cyanamides were prepared according to a previous method. 13 Other materials were purchased from Innochem (Beijing) Technology Co., Ltd. of China. Unless otherwise noted, all purchased chemicals were used without further purification.…”

“…12 Similarly, Chen's group developed a regioselective synthesis of N 2 -unprotected fivemembered cyclic guanidines through [3 + 2] annulation of aziridines and NCTS. 13 carbolines from alkyne−cyanamides or ynamide−nitriles with ynamides by a metal-free [2 + 2 + 2] cycloaddition process (Scheme 1e). 14 Despite some gains, developing a new cycloaddition reaction to various N-heterocycles from NCTS under mild conditions is highly desirable.…”

Organo-cyanamides: convenient reagents for catalytic amidation of carboxylic acids

“…7,8 In addition, the rupture of the N–S bond in NCTS has been developed for the deoxycyanamidation of alcohols, and 1,3-dipolar cycloaddition reactions (Scheme 1c, Path B). 9 To the best of our knowledge, a reaction involving a tandem N–S/C–N bond cleavage of NCTS has never been reported at the current stage. To further explore the reactivity of NCTS and based on our research interests in carboxylic acid conversion, 10 we herein disclosed an unusual desulfonylation/decynation reaction model of NCTS with carboxylic acids, allowing the rapid synthesis of amides in a highly efficient manner.…”

[8+3]‐Cycloaddition Reactions of Heptafulvenes or Azaheptafulvenes with α‐Halohydroxamates

“…α‐Halohydroxamates can also undergo [3+n]‐annulation via a tandem addition/intramolecular S N 2 cyclization pathway. Representative examples include the [3+2]‐cycloaddition of α‐halohydroxamate with cyclic imines, [18] alkenes, [19] or cyanamides, [20] as well as the [3+4]‐cycloaddition with stable or in situ‐ generated azadienes [21] . Based on our prior investigations on the chemistry of troponoid systems and α‐halohydroxamates, we envisioned that a formal [8+3]‐cycloaddition might take place readily between heptafulvenes or azaheptafulvenes with α‐halohydroxamates to yield a series of highly functionalized 7,6‐fused medium‐sized N‐containing heterocycles (Scheme 1c).…”