Visible-light-driven radical 1,3-addition of selenosulfonates to vinyldiazo compounds
作者:Weiyu Li、Lei Zhou
DOI:10.1039/d1gc02036f
日期:——
radical 1,3-selenosulfonylation of vinyldiazo compounds with selenosulfonates, providing various γ-seleno allylic sulfones in good yields. This photochemical reaction was carried out at room temperature in an open flask using ethyl acetate as the solvent without any photocatalysts or additives. The control experiments corroborated that the 1,3-addition proceeded via a radical-chain propagation process. The
carbene source, the seven‐membered rings upon subsequent hydrolysis and Cope rearrangement when 1,3‐dienes were used (see example). The α‐spirocyclopropyl lactones were formed with high E (trans) selectivity and high enantioselectivity, and cyclopropanation occurred at the terminal double bond in 1,3‐dienes with excellent regioselectivity.
A palladium-catalyzedcross-coupling reaction of aryliodides with cyclic vinyldiazo ester was developed. The reaction provides various 3-aryl-2-pyrones in good yields with high functional group tolerance. The synthetic application of the resulting 3-aryl-2-pyrones as the diene component in a Diels–Alder reaction was also described.
Vinyldiazolactone as a Vinylcarbene Precursor: Highly Selective C−H Insertion and Cyclopropanation Reactions
作者:Darren Bykowski、Kou-Hui Wu、Michael P. Doyle
DOI:10.1021/ja066452e
日期:2006.12.1
Vinylcarbenes are versatile synthetic intermediates, capable of asymmetric cyclopropanation and insertion into unactivated C-H bonds. The vinyldiazolactone precursor to the metal vinylcarbene possesses superior stability in comparison to previously known vinyldiazoacetates and, for the first time, allows the use of Z-vinylcarbenes in asymmetric C-H insertion and cyclopropanation reactions. Dirhodium azetidinone ligated compounds are optimal catalysts. Cyclopropanation coupled with the Cope rearrangement provides access to trans-3,4-disubstituted hydroazulenes.
Electrophile-Induced C–C Bond Activation of Vinylcyclopropanes for the Synthesis of <i>Z</i>-Alkylidenetetrahydrofurans
of vinylcyclopropanes as masked donor–acceptor system toward the stereoselective synthesis of Z-alkylidenetetrahydrofurans. Results of bromenium catalyzed indirect activation of C–C bond of vinylcyclopropanes and concomitant cyclization to alkylidenetetrahydrofuran and other heterocycles have been discussed. The stereoselectiveformation of the Z-isomer is strongly controlled by the extent of destabilization
我们对乙烯基环丙烷作为掩蔽的供体-受体体系对Z-亚烷基四氢呋喃的立体选择性合成的行为进行了详细研究。讨论了溴催化乙烯基环丙烷的C–C键的间接活化以及伴随环化成亚烷基四氢呋喃和其他杂环的结果。Z的立体选择性形成α-异构体受乙烯基环丙烷的一种薄纱构象异构体的去稳定程度的强烈控制。如在DA环丙烷的情况下,发现开环/环化步骤是立体特异性的。C–C键的活化导致紧密的碳共碳中间体,这从立体化学的完全保留中可以明显看出。构型的保留已通过必要的控制实验确定,该实验排除了双重倒置途径的可能性。目前的结果可作为直接的立体化学证据,以支持紧密的离子对中间体与有争议的S N 2途径。已在B3LYP / 6-31G(d)能级理论上进行了2D势能扫描,以获得构象异构体的相对能量。该ž在构象体的相对种群的基础上,对所观察到的选择性进行了解释,并对在M06–2x / 6-31 + G(d)水平上参与反应的中间和过渡态进行