Photolysis of 9-diazothioxanthene S,S-dioxide (9) in the presence of the substituted styrenes 11–15 gave the corresponding spirocyclopropane adducts 18–22 in high yield (67-86%), in addition to minor amounts of bi-9,9′-thioxanthenylidene S,S,S',S’-tetroxide (10). Laser flash photolysis of 9 produced a transient absorption (λmax324 nm) which was efficiently quenched by oxygen and was assigned to the carbene 2. This species was quenched by alcohols in a fast reaction attributable to the singlet state of 2, and in acetonitrile an ylide (24) was obtained. Quenching of 2 with the styrenes allowed the determination of the absolute rate constants for these reactions. The reactive spin state of 2 was investigated by studying the stereochemistry of the (1 + 2) cycloaddition of the carbene with trans-β-methylstyrene.
ASJC Scopus subject areas
- Organic Chemistry