Photoaddition of Alkenes to Conjugated α-Diketones: Tandem Cyclizations Leading to Tetrasubstituted Furans<sup>1</sup><sup>a</sup>
作者:Ashis K. Mukherjee、Paul Margaretha、William C. Agosta
DOI:10.1021/jo952079+
日期:1996.1.1
Photocycloaddition of 9a-c with 2 leads cleanly to tetrasubstituted furans 12a-c, respectively, in yields of similar to 85%. The reactive triplet is efficiently sensitized by 2-benzoylnaphthalene and quenched by anthracene, indicating that E(T) is in the range 43-58 kcal/mol. A mechanism is proposed involving an alkyl propargyl biradical (as 10) that closes first to a vinyl carbene (as 11) and then to product. Reaction of 9c with 20 furnishes only 22, and this result rules out an alternative mechanism in which the order of steps leading to the carbene is reversed.
Mukherjee Ashis K., Agosta William C., J. Chem. Soc. Chem. Commun, (1994) N 16, S 1821-1822
作者:Mukherjee Ashis K., Agosta William C.
DOI:——
日期:——
Tetrasubstituted furans from novel [3 + 2] photocycloaddition of conjugated acetylenic α-diketones with alkenes
作者:Ashis K. Mukherjee、William C. Agosta
DOI:10.1039/c39940001821
日期:——
Photocycloaddition of ketones 1a–c with tetramethylethylene2 furnishes tetrasubstituted furans 3a–c in isolated yields of ≈85%; a suggested mechanism for formation of 3a involves [3 + 2] cycloaddition by way of an initial biradical 5 to form an intermediate carbene 6, followed by cyclization to the furan.
酮的光环1A - c ^与四甲基2种配料四取代的呋喃3A - Ç中的≈85%分离产率; 提出的形成3a的机制包括通过初始双自由基5形成[3 + 2]环加成反应,形成中间体卡宾6,然后环化成呋喃。