Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
The syntheses of the tricarbonylchromium complexes 2 and 3 of 1-oxobenzocyclobutene and 1-hydroxybenzocyclobutene are described. Alcoholate 6 of 3 undergoes a ring opening to the corresponding ortho-quinodimethane intermediate between -30 and -20°C, which is trapped by dienophiles with high diastereoselectivity. While with most dienophiles products with a 1,2-cis configuration (7, 8, 10) are formed, vinyl sulfones react in an exo-selective cycloaddition with formation of 1,2-trans-configurated cycloadducts (12, 13). The configuration of the cycloadduct with phenyl vinyl sulfone is confirmed by an X-ray crystal structure analysis. As one of the important aspects of the chemistry of benzocyclobutene complexes is the chirality of compounds like 2 and 3, the enantiomeric resolution has been achieved via the semioxamazones of ketone 2.
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