Reactions of trimethylsilyl azide with heterocumulenes

Abstract

4b ;3',diisothiazole-1-carbonitrile (27). A solution of tetraethylammonium cyanide (1.7 g, 0.01 mol) in acetonitrile (50 mL) was added over a 15-min period to a solution of 26 (3.3 g, 0.01 mol) in acetonitrile (100 mL) at 15 °C, and crude 27 (2.21 g, 98%) was isolated by filtration. Compound 27 was washed with acetonitrile and ether. Recrystallization from n-butyl chloride (or acetone) gave analytically pure 28:

Nitropyridyl isocyanates in 1,3‐dipolar cycloaddition reactions

“…The carbonyl azide precursor was made in dry diethyl ether through diazotization of the corresponding carbonyl hydrazide. For our purpose the 1,3-dipolar cycloaddition with TMSA was performed in dry benzene, since the isocyanate was generated in this solvent, in contrast to the cycloaddition with phenyl isocyanate (1) which could be carried out without solvent using an excess of TMSA (two equivalents) [8]. In the present work 1-(3-nitropyridin-4-yl)-1H-tetrazol-5(4H)one (8) was obtained in 50 % yield after reflux overnight (Scheme 3).…”

“…Aryl isocyanates have been reported to react with either sodium azide [6,7] or trimethylsilylazide (TMSA) [8,9] to form 1-aryl-5(4H)-tetrazolinones (2) (Scheme 1). TMSA behaves as a 1,3-dipole in analogy to organic azides towards acetylenes [10], olefins [4][5]11] and nitriles [11,12].…”

“…The reaction of TMSA with heterocumulenes, such as isocyanates, isothiocyanates, carbodiimides and diphenylketene, has received little attention. It is, however, reported that 1,3-dipolar cycloaddition of phenyl isocyanate (1) to TMSA afforded 1-phenyl-5(4H)-tetrazolinone (2) in variable yields depending on the reaction conditions [8]. Equimolar amounts of TMSA gave 1,3-diphenylurea and phenylcarbamoylazide as byproducts in the reaction.…”

Mild and Efficient One-Pot Synthesis of 3,5-Disubstituted 1,2,4-Oxadiazoles from Nitriles Mediated by K3PO4

“…[12] Generally, five synthetic methods are used for the preparation of 1,2,4-oxadiazole scaffold: (i) cyclization of O-acylamidoxime formed from reaction of the amidoxime with a carboxylic acid or its activated derivative, [13] (ii) condensation of Nacylamidoximes, [14] (iii) 1,3-dipolar cycloaddition of nitriles to nitrile oxides, [15] (iv) oxidation of 4,5-dihydro-1,2,4-oxadiazoles [16] and (v) electrocyclic ring closure of nitrenoides. [17] More commonly, 1,2,4-oxadiazoles are prepared from amidoximes and carboxylic acid derivatives in two steps. In the first step, the amidoxime, prepared by the addition of hydroxylamine to a nitrile compound, is O-acylated by a carboxylic acid or its activated derivative; the heterocycle is subsequently formed by intramolecular cyclodehydration.…”

Synthesis of new 1-substituted 4-perfluoroalkyl tetrazol-5-ones

“…1,4-Disubstituted tetrazolin-5-ones are indirectly synthesized from reaction of azide ion [15] or trimethylsilylazide [16] with isocyanates. The reaction yields initially monosubstituted tetrazol-2-ones, which via an alkylation reaction, leads to the formation of a mixture of N-alkylation and O-alkylation products [17] (Scheme 1).…”