Jakob Oren

Novel bromination reagents · hexabromocyclopentadiene: bromination of activated saturated sites

Abstract Hexabromocyclopentadiene (HBC) readily brominates α-keto and benzylic sites, apparently by bromonium ion transfer.

Complete enantiospecificity in the highly regioselective and stereoselective photo- and thermal rearrangements of some homoconjugated ketones

Abstract The oxa-di-π-methane (ODPM) photorearrangement of 2-(carbomethoxy)spiro [5.5]undeca-1,3-diene-7-one ( 1 d) to 2 d and the latters thermal rearrangement to 3 d were shown to be not only fully regio-and stereoselective but also to occur with complete enantiospecificity. An additional example, the 2-hydroxymethyl derivative ( 1 f) was also studied and the two systems were chemically correlated.

Photochemistry of homoconjugated ketones: 2-(carbomethoxy)spiro[5.5]undeca-1, 3-dien-7-one.

Abstract The direct and sensitized irradiation of the title compound ( 2 c) was studied with particular attention to its oxa-di-π-methane rearrangement, the product of which is of notable structural and synthetic interest. X-ray diffraction data of the final product (8) are given to support structural assignments.

Unusual photorearrangements of homoconjugated diacylcyclohexa-2,4-dienes

The unprecedented triplet sensitized electrocyclic ring opening of various 3a,7a-diacyl-3a,7a-dihydroindans (3)–(5) to the corresponding cyclononatriene derivatives (7)–(11) is reported, direct irradiation at all absorbing wavelengths of the keto-ester (5) resulting in a diastereoselective oxa-di-π-methane (ODPM) rearrangement to the tricyclic product (6); dimethyl 1,2-dimethyl-1,2-dihydrophthalate (15) reacted similarly to give dimethyl E,E,E-2,7-dimethyl-2,4,6-octatrienoate (16), whose structure has been determined by single crystal X-ray diffraction analysis.