Photochemical cycloaddition of singlet and triplet diphenylvinylene carbonate with vinyl ethers

trans-Stilbene-amine exciplexes. Photochemical addition of secondary and tertiary amines to stilbene

“…It is shown to apply correctly to twelve 1-methyl tetra hydroisoquinolines of known absolute configuration, and is used to assign this in two cases where it is unknown. The 1,2,3,4-tetrahydroisoquinolines comprise an important group of natural products2 because of their biogenetic relationships to the morphine alkaloids. Many of the simple tetrahydroisoquinolines bear a substituent (usually methyl or benzyl) in the 1 position, and are optically active.…”

Photoadditions of aromatic compounds

“…38,200,202 For example, diphenylvinylene carbonate (120) adds to 1,3-dienes and to vinyl ethers to form cyclobutane adducts, the products being the same on direct and on sensitized (Michler's ketone) irradiation. 200,201 Typical products are those from cyclopentadiene and 2,5-dimethylhexadiene (121)(122)(123)(124).…”

“…Similar reactions are observed on irradiation of frans-a-phenylcinnamonitrile and 2,5-dimethyl-2,4hexadiene. 271 In nonpolar solvents (hexane, ether), all four possible isomeric 2 + 2 cycloadducts are formed (200)(201)(202)(203), and the reaction occurs via a singlet exciplex.…”

KeteneO,O-acetals

“…In the presence of an acetamide acetal, the latter provide y-0x0 esters (165) through the ketene a-aminoallyl ethyl acetal' '(164). When transesterification is camed out with orthoacetates, the intermediate (166) leads t o a p-allenic esterI9* (167)…”