Publication Date:
2012-11-07
Description:
The reaction of 3,5-bis(methoxycarbonyl)-4-oxo-4 H -pyrazole 1,2-dioxide (1a) with 1,3,5-cycloheptatriene (2b) gave a mixture of the novel endo -[4 + 6]-cycloadduct (4ab), anti-exo -[4 + 2]-cycloadduct (5ab), and the heterocage (6ab) derived from the intramolecular 1,3-dipolar cycloaddition reaction of the syn-endo -[4 + 2]-cycloadduct. Analogous endo -[4 + 6] selectivity in 1,3-dipolar cycloadditions has not been reported previously. The X-ray analysis indicates that 6ab has a very long N sp3 –N s p3 bond distance of 1.617(4) Å. The cycloaddition behaviour is discussed on the basis of transition-state structures optimized at the B3LYP/6-31G(d) level of theory, from which predictions of the peri-, regio-, and stereoselectivities agreed well with the experimental results. Copyright © 2012 John Wiley & Sons, Ltd. The reaction of 3,5-bis(methoxycarbonyl)-4-oxo-4 H -pyrazole 1,2-dioxide with 1,3,5-cycloheptatriene gave a mixture of the novel endo -[4+6]-cycloadduct, anti-exo -[4+2]-cycloadduct and the heterocage derived from the intramolecular 1,3-dipolar cycloaddition reaction of the syn-endo -[4+2]-cycloadduct. The cycloaddition behaviour is discussed on the basis of transition-state structures optimized at the B3LYP/6-31G(d) level of theory, from which predictions of the peri-, regio-, and stereoselectivities agreed well with the experimental results.
Print ISSN:
0894-3230
Electronic ISSN:
1099-1395
Topics:
Chemistry and Pharmacology
,
Physics
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