Tetrazole-1-oxides

Three 2-substituted tetrazole 1-oxides 550 representing the parent structure 548 (Scheme 163) have been reported (1913G71, 1983BAU181, 1984BAU142) (Scheme 165). These N-oxides are hygroscopic and crystallization with 0.5 mol of water has been observed. IR and H NMR data have been reported (1984BAU142). 

The 2-substituted tetrazole 1-oxides 550 were prepared from the corresponding hydroxytetrazoles 549 by methylation with trimethyloxonium tetrafluoroborate in CH2C12 at 20°C (1984BAU142) or by benzoylation of 1-hydroxytetrazole 549 (1913G71) (Scheme 165). Since N-alkylation and... 

The 2-substituted tetrazole 1-oxides 550 were readily deoxygenated by treatment with P + HI (1984BAU142). 

Substances 557 derived from structure 554 (Scheme 168) have been described (Scheme 169). The structure of 3-methyl-5-phenyl-tetrazole 1-oxide monohydrate 557 (R=Ph, Aik=Me, H20) has been determined by X-ray crystallography (1993PJC1767). H NMR, C NMR, and MS data are also available (1993PJC1767). 

Upon heating to 129°C 3-substituted tetrazole 1-oxides 557 rearranged into 4-substituted tetrazole 1-oxides 559, see Section 6.6. 

Three 4-substituted tetrazole 1-oxides 560 (Scheme 171) derived from the parent structure 559 (Scheme 170) have been described. H NMR, C NMR, 14N NMR, and 15N NMR data have been obtained (1989BAU1488). Line broadening of NMR signals provided information about the rate constant of the equilibrium between the A/-oxides 554 and 559 observed at elevated temperatures. 

Alkyl-substituted tetrazole 1-oxides 560 have been prepared by alkylation of the corresponding 1-hydroxytetrazole 555 with methylvinyl ketone to give a mixture of N-oxide 560 and the O-alkylated isomer 556 (1989BAU1488). Methylation of the A/-hyd roxytetrazole 555 with trimeth-yloxonium tetrafluoroborate afforded a mixture of N-oxide 560 (Alk=Me), an isomeric N-oxide of unknown structure, and the 1-methoxytetrazole 556 (Aik=Me) (1984BAU142) (Scheme 171). 

In another approach 3-substituted tetrazole 1-oxides 557 were isom-erized to the 4-substituted analogues 560 by heating to 120°C for 2h (1984BAU142) (Scheme 172). 

Heating 4-substituted tetrazole 1-oxides 560 gives rise to an equilibrium mixture of 560 with the corresponding 3-substituted isomer 557 (1989BAU1488). 

Substituted tetrazole 1-oxides 557 were N-dealkylated by treatment with K0H+AgN03 in ethanol solution with formation of 1-alkoxytetra-zoles 556 (1989BAU1488). 

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