Carbonyl compounds oxetane formation Paterno Biichi reaction

2 Carbonyl Compounds Oxetane Formation (Paterno-Biichi Reaction) 

The attack of n,Jt excited carbonyl compounds on electron-rich or electron-poor alkenes can be qualitatively different.892 893 Electron-rich alkenes preferentially interact with the electrophilic half-filled n-orbital on the oxygen atom, which is perpendicular to 

The lowest excited singlet states of aliphatic aldehydes and ketones have lifetimes on the order of nanoseconds, but they can be trapped by alkenes in a diffusion-controlled bimolecular oxetane formation. According to a theoretical study, a C-atom attack mechanism is either a concerted process producing oxetane directly or it involves a C—C bonded transient singlet biradical intermediate that rapidly cyclizes.896 The O-atom attack, in contrast, represents a nonconcerted path, allowing conformational motion of the shortlived intermediate thereby formed. 

Case Study 6.18 Synthesis of cage compounds - merrilactone A analogue 

Experimental details 02 An acetonitrile solution of 262 (0.54 him) was purged with nitrogen for 1 h. The solution was then immersed in an ice-bath and irradiated with a 

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Another photocycloaddition reaction that has been known for a long time is the Paterno-Biichi reaction, which involves the formation of oxetanes through the addition of an excited carbonyl compound to olefins ... 

The photocycloaddition of triplet benzophenone to norbornene was originally reported by Scharf and Korte. The photoproduct 101 that is formed in high exo-selectivity could be thermally cleaved to the 5,e-unsaturated ketone 102, an appHcation of the carbonyl-olefin metathesis (COM) concept. The 1,4-biradical formed in the interaction of norbornene with o-dibenzoyl-benzene was trapped in an intramolecular fashion by the second carbonyl moiety. A highly regioselective reaction of triplet benzophenone was reported with 5-methylenenorborn-2-ene, with preferential attack toward the exo CC double bond. A number of publications have discussed the photocycloaddition reactions of triplet carbonyl compounds to norbornadiene and quadricyclane, as weU as the competition between the Paterno-Biichi reaction and the sensitized norbornadiene/quadricyclane interconversion. Oxetane formation has also been reported for the photoreaction of biacetyl and para-quinones with benzvalene. ... 

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