Green Chemistry Strategies Using Crystal-to-Crystal Photoreactions:Stereoselective Synthesis and Decarbonylation of trams-alpha,alpha'-Dialkenoylcyclohexanones

摘要

Although photochemical crystal-to-crystal reactions have been documented since the early nineteenth century,most examples have been discovered by serendipity.It is only recently,and greatly motivated by the development of green chemistry,that chemists have begun systematic studies of synthetically promising crystal-to-crystal reactions.In a perfect setting,pure crystalline compounds would be activated to break and make bonds in a predictable manner.Multigram quantities of readily accessible crystalline reactants would be transformed into value-added crystalline products,perhaps by sunlight,with no need of external reagents or purification.Naturally,to reach this stage one must identify suitable reactions,develop mechanistic models to establish their generality,and ascertain the experimental feasibility of the method.With that in mind,we have recently explored the photodecarbonylation of crystalline ketones as a model with far-reaching potential.The reaction is suited to address one of the most important challenges in organic synthesis:the construction of adjacent stereogenic quaternary centers (Scheme 1).