Dimerization, Intermolecular Cycloaddition, and Reactions of Acetylenes

The three dimers (251 —253) are formed from the xylene-sensitized irradiation of cyclohexene. Regardless of the solvent used, the cis-trans-produci (252) predominates. It is reasoned that the dimers are produced by a non-stereospecific 

The two adducts (254) and (255) are formed from the irradiation of trans-stilbene in the presence of rra 5-3-phenylacrylonitrile. The two adducts are themselves photolabile and are converted into cis- and /ram-stilbene and cis- and 

See also references 64—66 for other examples of conformational control. 

Kitamura, S. Toki, and H. Sakurai, Kokagaku Toronkai Koen Yoshishu, 1979, 190 (Chem. Abstr., 1980, 93, 70806). 

The benzophenone-sensitized addition of chlorofluoro-olefins (262) to indene has been studied. The identity of the adducts (263) was established by detailed spectroscopic analysis. The mechanism of the addition is believed to involve biradicals such as (264). 

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