Reaction Control in Synthetic Organic Photochemistry: Switching between [5+2] and [2+2] Modes of Cycloaddition
作者:Claudio Roscini、Kara L. Cubbage、Malcolm Berry、Andrew J. Orr-Ewing、Kevin I. Booker-Milburn
DOI:10.1002/anie.200904059
日期:2009.11.2
Split personality: Reaction conditions that enable powerful control over the mode of photocycloaddition in maleimides have been developed. Direct irradiation favors the [5+2] mode whereas sensitized irradiation allows a complete switch to the [2+2] mode (see scheme; TBS=tert‐butyldimethylsilyl).
to high stereoselectivity being observed for 13e and 13g, respectively. Use of cyclic alkene side chains led to the formation of tri- and tetracyclic products with high degrees of stereoselectivity in most cases. Some of the polycyclic ring systems that were prepared constitute the core skeleton of a number of complex alkaloids. The substrate 29 underwent an unexpected [2+2] photocycloaddition to yield
许多 N-链烯基取代的马来酰亚胺衍生物的紫外线照射导致以极好的产率形成复杂的全氢氮杂茚。整个过程可以被认为是一个正式的分子内 [5+2] 环加成。通过合适的烯醇与各种马来酰亚胺的Mitsunobu偶联制备底物。烯基侧链的甲基取代以良好的产率得到环加合物 13a-g,分别对 13e 和 13g 观察到中等至高的立体选择性。在大多数情况下,环状烯烃侧链的使用导致形成具有高度立体选择性的三环和四环产物。一些已制备的多环系统构成了许多复杂生物碱的核心骨架。
Reaction Optimization and Mechanism in Maleimide [5 + 2] Photocycloaddition: A Dual Approach Using Tunable UV Lasers and Time-Dependent DFT
作者:David M. E. Davies、Craig Murray、Malcolm Berry、Andrew J. Orr-Ewing、Kevin I. Booker-Milburn
DOI:10.1021/jo062316g
日期:2007.2.1
An in-depth study of the intramolecular [5 + 2] photocycloaddition of maleimides using tunable UV lasers has demonstrated that the peak in quantum yield and rate both occur at wavelengths some 50 nm red shifted from the maxima observed in the UV spectra. A detailed explanation for these findings using time-dependent DFT calculations is presented, and the implications for a previously adopted mechanism
Rapid Access to Azepine-Fused Oxetanols from Alkoxy-Substituted Maleimides
作者:Kevin I. Booker-Milburn、James R. Baker、Ian Bruce
DOI:10.1021/ol049645k
日期:2004.4.1
UV irradiation of alkoxy-substituted N-alkenylmaleimides induces a sequence involving a [5 + 2] cycloaddition followed by a Norrish-Yang cyclization. The resulting highly strained alkylidene oxetanol-fused azepines are formed in good yield and with high diastereoselectivities.
A Practical Flow Reactor for Continuous Organic Photochemistry
作者:Benjamin D. A. Hook、Wolfgang Dohle、Paul R. Hirst、Mark Pickworth、Malcolm B. Berry、Kevin I. Booker-Milburn
DOI:10.1021/jo050705p
日期:2005.9.1
Compact flow reactors have been constructed and optimized to perform continuous organic photochemistry on a large scale. The reactors were constructed from commercially available or customized immersion well equipment combined with LTV-transparent, solvent-resistant fluoropolymer (FEP) tubing. The reactors were assessed using the [2 + 2] photocycloaddition of malemide 1 and 1-hexyne forming the cyclobutene product 2 and the intramolecular [5 + 21 photocycloaddition of 3,4-dimethyl-1-pent-4-enylpyrrole-2,5-dione 3 to form the bicyclic azepine 4. The reactors were shown to be capable of producing > 500 g of 2 and 175 g of 4 in a continuous 24 h processing period. Due to the facile control of irradiation time, the continuous flow reactor was also shown to be superior to a batch reactor for performing a problematic photochemical reaction on a larger scale.