Cyclohexenes photochemical addition reactions

Photochemical addition of dimethyl acetylenedicarboxylate to the enamine H2C=CE-NH-CE=CH2 (E = COOMe) yields the bridged cyclohexene (90), which decomposes at 90 °C in a retro-Diels-Alder reaction to ethylene and the ester (91). 

Photochemical addition of dimethyl acetylenedicarboxylate to the enamine H2Ca C -NH-CE=>CH2 (E => COOMe) yields the bridged cyclohexene (90), irtiich decomposes at 90 °C in a retro-Diels-Alder reaction to ethylene and the ester (91). The adducts (92 R = PhCO or COOBu ") of perf luorobut-2-yne, CP CHCCF, to N-substituted pyrroles have been degraded to 3,4-bls(trlfluoromethyl)pyrroles (93) by two methods in the former, the adducts were first hydrogenated at the unsubstituted double bond and then heated to eliminate ethylene,idille in the latter, the adducts were treated with mesitonitrile oxide, 2,4,S-Me C H CEN -0, which removed the ethylene unit in the form of the isoxazole (94). ... 

Efficient and diastereoselective additions to cyclohexene were observed in the photochemical reaction with ethyl chlorocarbamate in dichloromethane76 and in the reaction with several alkyl chlorocarbamates in the presence of chromium(II) chloride77-79. Here, the reaction mechanism involves the formation of an amidyl radical complexed with chromium(III). 

A careful study of the formation of thiolesters R R CH CO SR , by the addition of a thiol to a keten, suggests that a radical path is followed. At least this accounts for the very irreprodudble rates. Photochemical reactions of 2-aminothiophenol (25) with carboxylic acids or cyclohexene provide a challenge from a mechanistic point of view the. S-methyl... 

Cyclohexene-1-carboxylic acid, its methyl ester, or its nitrile undergo very slow photochemical [2+ 2] addition with electron-rich olefins such as tetramethyl-ethylene. The [2 -f 2] products are usually accompanied by those of ene-like reactions. 

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