1.3.5.7- Tetraazadecalins, conformational studies

Both theoretical and experimental studies have been reported for as- and /ra r-l,3,5,7-tetraazadecalin systems 66 and 67 <1996AJC285, 1998JOC8850>. The former is reportedly more stable as the iV-inside form 66a (calc. AH( 29.6 kj mol ) than as the A -outside form 66b (calc. AH( 56.3 kj mol ), although the two forms exist in equilibrium. The more crystalline trans-form 67 again exists in two all-chair conformations, 67a and 67b, of which the former (calc. AH I 37.8 vs. 46.1 kJ mol for R = H) is more stable <1996AJC285>. The conformational effect of changing the 2- and 6-substituents is reportedly small. 

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