engleski

Intramolecular 1, 3-dipolar cycloadditions of the new sydnone derivatives

Inter- and intramolecular photochemical [2+2] cycloaddition reactions of o-substituted divinylbenzene with furan and pyrrole rings give various hetero polycyclic compounds (1). The photochemical reaction of the sydnone analogue 1 did not undergo intramolecular cycloaddition (2), but in the presence of acrolein, the intermolecular 1, 3-dipolar cycloaddition products 2 and 3 were isolated. Photochemically induced intramolecular 1, 3-dipolar cycloaddition of 4a and 4b produced the same diazacyclopentalene derivative, as the main product. The thermal intramolecular cycloaddition of 4a and 4b did not give expected two isomeric cycloadducts, but two different products. Identification of the products as well as the reaction mechanism will be discussed.

1; 3-dipolar cycloadditions; intermolecular reactions; intramolecular reactions; sydnones; stilbenes; photochemistry; heterocycles

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