Department of Chemistry, Temple University, 1901 N. 13th St., Philadelphia, PA, 19122, USA.
Theravance Biopharma U.S., 901 Gateway Boulevard, South San Francisco, CA, 94080, USA.
Angew Chem Int Ed Engl. 2017 Jan 2;56(1):319-323. doi: 10.1002/anie.201608684. Epub 2016 Nov 30.
Irradiation of a 1,3-enyne tethered to a 2-pyridone, in the presence of oxygen, leads to formation of a seven-membered ring product, an overall [4+4-1] reaction. This transformation involves two unstable intermediates and a sequence of unusual reactions. An initial [4+4] photocycloaddition of the enyne with the pyridone yields a 1,2,5-cyclooctatriene. Photooxidation of this triene forms a cyclopropanone and subsequent photoextrusion of carbon monoxide gives the observed 1,4-cycloheptadiene product. The first-formed cyclooctatriene and the cyclopropanone could be observed and characterized spectroscopically. The cyclopropanone underwent CO extrusion both photochemically and thermally to give the cycloheptadiene product. Addition of fluoride or acetylide to the most stable cyclopropanone occurred chemoselectively at the two different silicon groups rather than the carbonyl group. The resulting cyclopropanone ring openings gave unsaturated aldehydes.
在氧气存在的情况下，将 1,3-烯炔键合到 2-吡啶酮上进行辐照，导致形成七元环产物，这是一种总体上的 [4+4-1] 反应。这种转化涉及两个不稳定的中间体和一系列不寻常的反应。烯炔与吡啶酮的初始 [4+4] 光环加成生成 1,2,5-环辛三烯。该三烯的光氧化形成环丙酮，随后一氧化碳的光解逐出得到观察到的 1,4-环庚二烯产物。首先形成的环辛三烯和环丙酮可以通过光谱学观察和表征。环丙酮可以通过光化学和热化学两种方式进行 CO 逐出，得到环庚二烯产物。氟化物或炔烃加成到最稳定的环丙酮上，优先在两个不同的硅基团而不是羰基上发生化学选择性加成。所得的环丙酮开环得到不饱和醛。
