Synthesis, effect of substituents on the regiochemistry and equilibrium studies of tetrazolo[1,5-a]pyrimidine/2-azidopyrimidines

Abstract

An efficient synthesis methodology for a series of tetrazolo[1,5-a]pyrimidines substituted at the 5- and 7-positions from the cyclocondensation reaction [CCC + NCN] was developed. The NCN corresponds to 5-aminotetrazole and CCC to β-enaminone. Two distinct products were observed in accordance with the β-enaminone substituent. When observed in solution, the compounds can be divided into two groups: (a) precursor compounds with R = CF3 or CCl3, which leads to tetrazolo[1,5-a]pyrimidines in high regioselectivity with R at the 7-position of the heterocyclic ring; and (b) precursor compounds with R = aryl or methyl, which leads to a mixture of compounds, tetrazolo[1,5-a] pyrimidines (R in the 5-position of the ring) and 2-azidopyrimidines (R in the 4-position of the ring), which was attributed to an equilibrium of azide–tetrazole. In the solid state, all compounds were found as 2-azidopyrimidines. The regiochemistry of the reaction and the stability of the products are discussed on the basis of the data obtained by density functional theory (DFT) for energetic and molecular orbital (MO) calculations.

Synthesis of (E)-5-Arylvinyl-7-methyltetrazolo[1,5-a]pyrimidines

“…The bond lengths and bond angles in the molecule have the typical values, with the exception of the slightly distorted C 3 C 2 C 6 angle, 127.9(2)°. A similar deviation of the bond angle from 120°, leading to a shift of the methyl group C 6 H 3 towards the tetrazole ring, is also typical for other alkylsubstituted tetrazolopyrimidines [14,15]. Only 5,6-dimethyltetrazolo[1,5-a]pyrimidine 3 was obtained, when carrying out a three-component reaction under milder conditions in the presence of sodium hydrogen sulfate in methanol according to the previously described method [16].…”

Synthesis of Substituted Pyrimido[1,2‐b]indazoles through (3+2+1) Cyclization of 3‐Aminoindazoles, Ketones, and N,N‐Dimethylaminoethanol as One‐Carbon Synthon

“…1). The reaction might proceed via the (3+2+1) cycloaddition to provide an intermediate 3 n′ which existed a tetrazole‐azido equilibrium [21] with its azido isomer ( 3 n’′ ) and followed by a removal of N 2 upon heating to afford 4 . Furthermore, β‐diketones and its derivative such as dibenzoylmethane ( 2 g′ ), benzoylacetone ( 2 h′ ) and ethyl benzoylacetate ( 2 i′ ) were attempted to replace acetophenone ( 2 a ) for the conversion and surprisingly the expected 3‐carboxyl pyrimido[1,2‐ b ]indazoles were not afforded.…”

Synthesis and Study of Steering of Azido-tetrazole Behavior in Tetrazolo[1,5-c]pyrimidin-5-amine-Based Energetic Materials

“…Researchers continuously work on factors such as nature of the substituents (electrondonating or electron-withdrawing groups), solvent (polar or nonpolar), temperature (low or high), and physical state of the compound (solid-state or solution) that have the most influence on the steering of azide−tetrazole equilibrium and is attracting attention over time by the development of vast knowledge as a result of new findings. 14,15 Energetic organic materials normally consisting of CHON tend to be nitrogen-rich which increases the energetic properties by releasing dinitrogen gas upon detonation and overcoming the drawback of environmental threats. 16 During the initiation of the energetic organic materials, the breakage of bonds among C−N, N−N, or N = N leads to the rapid release of energy, which results in high detonation and favorable thermal stability.…”