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Preparation of TADOOH, a Hydroperoxide from TADDOL, and Use in Highly Enantioface‐ and Enantiomer‐Differentiating Oxidations
Author(s) -
Aoki Masao,
Seebach Dieter
Publication year - 2001
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(20010131)84:1<187::aid-hlca187>3.0.co;2-o
Subject(s) - chemistry , enantiomer , kinetic resolution , bicyclic molecule , adduct , alcohol , catalysis , stereochemistry , diol , medicinal chemistry , organic chemistry , enantioselective synthesis
Replacement of one OH group in TADDOL (= α , α , α ′, α ′‐tetraaryl‐1,3‐dioxolane‐4,5‐dimethanol) by an OOH group gives a stable, crystalline chiral hydroperoxy alcohol TADOOH (={(4 R ,5 R )‐5‐[(hydroperoxydiphenyl)methyl]‐2,2‐dimethyl‐1,3‐dioxolan‐4‐yl}diphenylmethanol) 3 , the crystal structure of which resembles those of numerous other TADDOL derivatives ( Fig. 2 ). The new hydroperoxide was tested as chiral oxidant in three types of reactions: the epoxidation of enones with base catalysis ( Scheme 2 ), the sulfoxidation of methyl phenyl sulfide ( Scheme 3 ), and the Baeyer‐Villiger oxidation of bicyclic and tricyclic cyclobutanones, rac ‐ 10a – d with kinetic resolution ( Scheme 4 , Fig. 3 , and Table ). Products of up to 99% enantiomer puritiy were isolated (the highest values yet observed for oxidations with a chiral hydroperoxide!). Mechanistic models are proposed for the stereochemical courses of the three types of reactions ( Schemes 5 and 6 , and Fig. 4 ). Results of AM1 calculations of the relative transition‐state energies for the anionic rearrangements of the exo Criegee adducts of TADOOH to the enantiomeric bicyclo[3.2.0]heptan‐6‐ones are in qualitative agreement with the observed relative rates ( Table and Fig. 5 ).