Synthesis, X-ray and conformational studies of novel tetrazole-containing macrocycles: 4,13-dioxa-1,7,8,9,17,18,19,20-octaazatricyclo[14.2.1.17,10]icosa-8,10(20),16(19),17-tetraene and 4,14-dioxa-1,7,8,9,10,18,19,20-octaazatricyclo[15.2.1.07,10]icosa-8,10,17(20),18-tetraene

Abstract

Alkylation of 1,5-bis(tetrazol-5-yl)-3-oxapentane by 2,2′-dichlorodiethyl ether under conditions of high dilution led to two isomeric crown-like macrocycles: 4,13-dioxa-1,7,8,9,17,18,19,20-octaazatricyclo[14.2.1.1^7,10]icosa-8,10(20),16(19),17-tetraene 2 and 4,14-dioxa-1,7,8,9,10,18,19,20-octaazatricyclo[15.2.1.0^7,10]icosa-8,10,17(20),18-tetraene 3. The crystal structures of both compounds were determined. In the crystalline state, macrocycle 2 exists in syn-form with a symmetry near C_s, whereas macrocycle 3 has only C₁ symmetry. The latter was observed to adopt two different conformations in the crystalline state. An AM1 conformational analysis of macrocycle 2 revealed 30 different conformations, one of which is similar to the observed crystal structure.