Generation and reactivity of N,N‐dimethylaminobenzotriazolylcarbene a new nucleophilic carbene

Abstract

N,N‐Dimethylaminobenzotriazolylcarbene (5) reacted with phenyl isocyanate in a [1+2+2] cycloaddition and then with nucleophiles to generate various hydantoins 10 in a one‐pot procedure. It was also found that this novel carbene reacted with trans‐dibenzoylethylene (11) in a [1+4] cycloaddition, generating 2‐dimethylamino‐3‐benzoyl‐5‐phenylfuran (13) and 2‐phenyl‐3‐[benzotriazol‐1‐yl]‐4‐benzoylfuran (14) whose structures were confirmed by 1H‐13C long range correlations as well as the structure of furan 14 being confirmed by X‐ray crystallography.

Benzotriazole-Mediated Synthesis of Nitrogen-Containing Heterocycles

“…Subsequent treatment of 191 with nucleophiles provided products 192 stereoselectively keeping the trans-relative stereochemistry of the substituents on C-4 and C-5 of the starting material (Scheme 70) [147]. When the Vilsmeier-type salt 145 [121] is treated with triethylamine, it generated an aminocarbene, which underwent [1+2+2] cycloaddition with phenylisocyanate to give imidazolidine-2,4-diones 193. Quenching the reaction with tetraethylammonium sulfide resulted in reduction of the functionality on C-5 to give 1,3-diphenylhydantoin 194.…”

“…Vilsmeier-type salt 145 [121] reacted readily with conjugated β-enaminonitriles to give tetrasubstituted pyridines 288. The reaction appeared to proceed through intermediate 287, as such structures can be identified in the reaction mixture before their treatment with a base (Scheme 106) [197].…”

“…The most popular method for the preparation of pyrazoles unsubstituted at the nitrogen atoms involves condensation of hydrazine with β-dicarbonyl compounds. Easily accessible synthons for β-dicarbonyl compounds are enamine-iminium salts 146, prepared from a Vilsmeier-type salt 145 [121] and N-propylimines. Treatment of 146 in situ with hydrazine gave 3,4-disubstituted pyrazoles 147 (Scheme 50) [122].…”

Benzotriazole-Mediated Synthesis of Oxygen-Containing Heterocycles

“…This method provided a convenient alternative to other oxadiazole synthetic approaches utilizing acyl halides [72]. The versatile and stable benzotriazole Vilsmeier-type reagent 219 [37] was used in combination with aroyl hydrazides 218 for the high-yielding and convenient preparation of 1,3,4-oxadiazoles 220 (Scheme 45) [73]. Similarly, di(benzotriazol-1-yl)methanimine 221 was successfully utilized for the preparation of 2-amino-5-aryl-1,3,4-oxadiazoles 222 from hydrazides 218 [74].…”

“…It involved an acyclic aminocarbene 88, generated by deprotonation of N,N-dimethylaminobenzotriazolylmethyleniminium chloride 87 under mild conditions. Trapping of the carbene with trans-dibenzoylethylene 89 afforded 2-phenyl-3-[benzotriazol-l-yl]-4-benzoylfuran 91 and 2-dimethylamino-3-benzoyl-5-phenylfuran 92 via a [1+4] cycloaddition (Scheme 20) [37].…”