Schenck ene reaction

This problem was solved by Adam and coworkers in 1994-1998. They presented a high-yielding and diastereoselective method for the preparation of epoxydiols starting from enantiomerically pure allyhc alcohols 39 (Scheme 69). Photooxygenation of the latter produces unsaturated a-hydroxyhydroperoxides 146 via Schenck ene reaction. In this reaction the (Z)-allylic alcohols afford the (5, 5 )-hydroperoxy alcohols 146 as the main diastereomer in a high threo selectivity (dr >92 8) as racemic mixmre. The ( )-allylic alcohols react totally unselectively threolerythro 1/1). Subsequent enzymatic kinetic resolution of rac-146 threolerythro mixture) with horseradish peroxidase (HRP) led to optically active hydroperoxy alcohols S,S) and (//,5 )-146 ee >99%) and the... 

Prein, M., Adam, W. The Schenck ene reaction diastereoselective oxyfunctionalization with singiet oxygen in synthetic appiications. 

The addition of singlet oxygen to isoquinoline-1,3-diones (132) yields the triketone (133) via a Schenck ene reaction and the benzoisofuranone (134) via a 4 - - 2-cycloaddition (Scheme 51). The Diels-Alder addition of singlet oxygen to cis-3,8-dihydroheptalene-3,8-dicarboxylate (135) yields a mono-addition product (136), which on further addition of a second singlet oxygen produces jyn-bis(norcaradiene) bis(endoperoxide) (137) (Scheme 52). ... 

Following the discovery of the ene reaction of singlet molecular oxygen ( Ap (Scheme 15) in 1953 by Schenck [88], this fascinating reaction continues to receive considerable mechanistic attention today. The importance of a path via the perepoxide intermediate or a perepoxide-Iike transition state [13] or the perepoxide quasi-intermediate [70] was proposed for the ene reactions of singlet oxygen with alkenes affording allylic hydroperoxides. 

D. Mechanism of ene reaction. In the ene reaction, the double bond is shifted to the allyl position with respect to the starting material according to the scheme proposed by Schenck. This involves (i) attachment-of the oxygen molecule to one of the carbon atoms of the double bond (e.g. CJ, (ii) shift of the double bond to allyl position (e.g. to C -> Cj) and (iii) migration of the allyl hydrogen atom to the terminus of the peroxy group. 

The ene reaction of singlet oxygen with alkenes was originally discovered [22,23] by Schenck in 1943. It is of synthetic [21,24], biochemical [25-27], and environmental significance [25,28] (Scheme 1). Over the years, the mechanism of this re-... 

Quasi, H., Dietz, T, and Witzel, A., Tetra(2,6-dichlorophenyl)porphyrin a superior sensitizer for the singlet-oxygen ene reaction (Schenck reaction), Liebigs Ann., 1495,1995. 

The reaction of aromatics later had an important role in defining the mechanism of the photochemical reacticMis with oxygen, but had a limited synthetic significance. From this point of view, a big step forward was the development by Schenck of the wide-scope photosensitized oxygen addition to dienes to form l,2-diox-4-enes and to alkylalkenes to form propenyl-3-hydroperoxides [99—101]. 

Brilnker, H.-G. and Adam, W., Diastereoselective and regioselective singlet oxygen ene oxyfunc-tionalization (Schenck reaction) photooxygenation of allylic amines and their acyl derivatives,/. Am. Chem. Soc., 117, 3976,1995. 

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