A New Resolution Procedure for the Preparation of Both (R)-(+)- and (S)-(-)-4-tert-Butoxycyclopent-2-enone from Racemic 4-tert-Butoxycyclopent-2-enone and Conversion of (R)-(+)-Butoxycyclopent-2-enone into (R)-(+)-4-Acetoxycyclopent-2-enone. A New Method for the Determination of the ...

Article abstract of DOI:10.1021/jo00015a035

(1S)-(-)-10-Mercaptoisoborneol undergoes conjugate addition to (+/-)-4-tert-butoxycyclopent-2-enone in methanol containing N,N,N',N'-tetramethylethylenediamine to give a 1:1 mixture of diastereomers of 3-tert-butoxy-4-<<(exo-2'-hydroxy-7',7'-dimethylbicyclo<2.2.1>heptanyl)methyl>thio>cyclopentanone in 93-95percent yield.The mixture is converted by m-chloroperbenzoic acid into the corresponding sulfoxide mixture.The (3R,4R,R_S)-sulfoxide isomer, whose absolute configuration has been determined by X-ray crystallography, crystallizes cleanly from this mixture in an enantiomeric yield of 76percent from the corresponding sulfide.It is decomposed on silica gel to generate (R)-(+)-4-tert-butoxycyclopent-2-enone, with an enantiomeric purity of >/- 99.9percent in 92percent yield from the sulfoxide, and 10-thiodiisobornyl 10'-sulfoxide.Similarly, the (S)-(-)-enone is prepared from (1R)-(+)-10-mercaptoisoborneol.The (+/-) and the (R)-(+)-enone, respectively, are converted by a catalytic amount of FeCl3 in acetic anhydride into (+/-) and (R)-(+)-4-acetoxycyclopent-2-enone (with an enantiomeric purity of >/- 99.9percent) in 80percent yield.The enantiomeric purity of the products was assessed through their treatment with (-)-10-mercaptoisoborneol and analysis of the adducts by HPLC and 400-MHz 1H NMR spectroscopy.