Photofragmentation via single-electron transfer: selective labilization of carbon-carbon bonds in amino alcohols with several bonds between heteroatom substituents
作者:Xiaohong Ci、David G. Whitten
DOI:10.1021/ja00191a069
日期:1989.4
compounds is observed to proceed very cleanly via relatively low energy excitation, an interesting question is whether a correspondingly clean C-C bond fragmentation can occur in molecules in which two heteroatoms are separated by greater distances. Here they report results that indicate selective cleavage can occur for vinylogous aminoalcohols and related compounds via pathways that involve both net reduction
最近的一些研究表明,α},β}-二杂原子取代的有机物的氧化光碎裂可以作为单电子转移的结果发生。光氧化还原过程虽然涉及自由基离子中间体,但与 2 电子 Grob 碎裂非常相似。对各种电子受体和氨基醇的机理研究表明,受体阴离子自由基碱度和阳离子自由基中 CC 键能的显着降低都导致了低 (2.5-5 kcal/mol) 的离子裂解活化能 -激进对。由于α},β}-二杂原子取代的化合物的反应被观察到通过相对低能量的激发非常干净地进行,一个有趣的问题是,在两个杂原子相距较远的分子中是否会发生相应干净的 CC 键断裂。在这里,他们报告的结果表明,乙烯基氨基醇和相关化合物可以通过涉及光激发受体的净还原和催化作用的途径发生选择性裂解。
A Convenient Synthesis of Unsymmetrical Pinacols by Coupling of Structurally Similar Aromatic Aldehydes Mediated by Low-Valent Titanium
pinacol-type couplings between two structurally similar aromatic aldehydes promoted by low-valenttitanium generated unsymmetrical pinacols in moderate to good isolated yields in an erythro/threo ratio of up to 91:9. This synthetic methodology significantly extends the scope of the cross pinacol-type couplings. pinacol - pinacol-type coupling - cross coupling - McMurry coupling - low-valenttitanium