Cyclopropenyl azides, rearrangement

Thermolytic rearrangement of 1,2,3-trisubstituted cyclopropenyl azides constitutes the only proven method at present for the preparation of monocyclic 1,2,3-triazines, and both the generality and validity of the procedure have been established. Thus, a substantial number of derivatives of the type 2, R = alkyl, aryl, have now been prepared, and X-ray crystallographic analysis has confirmed the structures of the products (see Section II, D, 2). Thermolysis of triarylcyclopropenyl... 

The rearrangement of cyclopropenyl azides (396) is used for the synthesis of monocyclic 1,2,3-triazines (397) (73JOC3149, 79CB1514). However, the most general method is the oxidation of N-aminopyrazoles (398) with lead tetraacetate or variety of other oxidants (92AHC(53)85). 

Cyclopropenylium ions 5 with tert-butyl or aryl substituents reacted with azide ion to give the covalent cyclopropenyl azides The triaryl derivatives 8 readily rearranged to the... 

The second method for the synthesis of monocyclic aromatic 1,2,3-triazines 2 by ring enlargement is the rearrangement of cyclopropenyl azides i78-86"89-"7- 124 (cf. Houben-Weyl, Vol. E 17d, p2849), by heating them neat,78-89,117-118 in methanol,86 89 dimethylformamide,89 benzene,86119 toluene,86 xylene,88-120 or dichloromethane.87 121 The only limitation to this method seems to be the availability of the cyclopropenylium salts as starting materials for the cyclopropenyl azides. Cyclopropenyl azides may be generated in situ from a cyclopropenylium salt and sodium or potassium azide.86 89... 

Method B By Rearrangement of Cyclopropenyl Azides 1 86 The cyclopropenyl azide (10 mmol) in benzene (20 mL) was heated to reflux for 5 h. The solvent was evaporated and the residue purified by column chromatography. 

There are two general synthetic methods for 1,2,3-triazines which belong to this section. The first, reported in 1960 <60TL19>, is the thermal rearrangement of a cyclopropenyl azide (115) (Equation... 

This transformation can be effected by lead tetraacetate or nickel peroxide. (2) Thermal rearrangement of cyclopropenyl azides 10 ... 

This rearrangement takes place even under mild conditions. The cyclopropenyl azides 10 are accessible from cyclopropenylium ions and NaN3. 

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