Development and Synthetic Application of a Novel Type of α-Phosphonocyclobutanones and α-Phosphonoazetidinones

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Recently, the rhodium(II)-catalyzed intramolecular C-H insertion of α-diazo carbonyl compounds has been widely studied and found to be great of value. Reported herein is the synthesis of α-phosphonocyclobutanones bearing 9,10-dihydro-9,10-ethanoanthracene moiety via rhodium(II)-catalyzed intramolecular insertion reaction. 11-Methyl- (3b), 11-ethyl- (3c), and 11-propyl-11-(dimethylphosphono)-acetyl-9,10-dihydro-9,10-ethanoanthracene (3d) were prepared from the Diels-Alder adducts of anthracene and methyl acrylate derivatives, and dimethyl lithiomethylphosphonate in good yields. Α-Diazo β-keto phosphonates 4b-d were readily prepared from 3b-d according to the conventional diazo transfer method by the use of p-toluenesulfonyl azide. Catalytic decomposition of f4b-d was carried out in ClCHィイD22ィエD2CHィイD22ィエD2Cl containing RhィイD22ィエD2(Oac)ィイD24ィエD2 at 80℃ to afford the mixture of cyclobutanones 5b-d and cyclopentanones 6c,d. The stereochemical assignment of 7,8 : 9,10-dibenzo-2-ethyl-4-(dimethylphosphono)tricyclo[4.2.2.0ィイD22,5ィエD2]deca-7,9-dien-3-one (5c) was made on the basis of their ィイD11ィエD1H NMR and IR spectral data. That is, the IR spectrum of 5c shows a peak for carbonyl absorption at 1774.7 cmィイD1-1ィエD1. The ィイD11ィエD1H NMR spectrum of 5c shows a signal for methyl (t, J=4.9 HィイD2ZィエD2, 3H) at δ1.09 and a signal for methine (d, J=3.9 HィイD2ZィエD2, 1H) of 6-position at δ4.51. Accordingly, cyclobutanones were exclusively produced via insertion into the ethane bridge methylene C-H bonds. A similar decomposition of 4b-d with chiral Rh(II) catalysts, such as RhィイD22ィエD2[N-Phtn-(L)-Phe]ィイD24ィエD2 and RhィイD22ィエD2[N-Phth-(L)-Ala]ィイD24ィエD2, afforded the desired optically active 5b-d up to 43%ee. In this reaction, the use of RhィイD22ィエD2[N-Phth-(L)-Phe]ィイD24ィエD2 gave the optically active 5b-d in higher optical yield than that of RhィイD22ィエD2[N-Phth-(L)-Ala]ィイD24ィエD2 irrespective of the kind of alkyl substituents at 11-position of diazo compounds 4b-d.