The suitability of enantiomerically pure deltacyclenes as tacyclane-derived phosphorus ligands were synthesized. building blocks in the synthesis of expanded phosphanes They were tested in the Rh-catalyzed asymmetric hydrogewas examined. Different substituted deltacyclenes were irra-nation of (Z)-(a)-N-acetamidocinnamic acid and in the Pddiated with diphenylphosphane and three bisphosphanyl de-catalyzed asymmetric allylation of 1,5dimethylbarbituric rivatives. With these P-H addition reactions. new chiral del-acid.
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1994 stereochemistry stereochemistry (general, optical resolution) O 0030
-038Asymmetric 1,3-Dipolar Cycloaddition of Nitrones with Ketene Acetals Catalyzed by Chiral Oxazaborolidines.-The nitrones (III) or (VI) and ketene acetals (II) or (VII) undergo an asym. 1,3-dipolar cycloaddition in the presence of catalytic oxazaborolidines (I) and (V). The resulting isoxazolidines are obtained in high yield and regioselectivity but, in general, with low enantioselectivity. Mild hydrogenolysis of the cycloadducts affords suitable synthons for imporant classes such as the isoquinoline (VIII), intermediate for biologically active compounds. -(SEERDEN, J.-P. G.; SCHOLTE OP REIMER, A. W. A.; SCHEEREN, H. W.; Tetrahedron Lett. 35 (1994) 25, 4419-4422; Dep. Org. Chem., Univ. Nijmegen, NL-6525 ED Nijmegen, Neth.; EN)
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