Cycloadditions between nitrile oxides and cis-4-benzoylamino-2-cyclopenten-1-ol offer an example in which a strong intramolecular hydrogen bond completely offsets the syn-directing ability of the cyclopentene substituents. Solvents affected the conformational equilibrium of the cyclopentene dipolarophile but did not sizeably influence the cycloaddition selectivity, showing the absence of directing
Design, Synthesis, and Conformational Analysis of Proposed β‐Turn Mimics from Isoxazoline‐Cyclopentane Aminols
作者:Misal Giuseppe Memeo、Mariella Mella、Valentina Montagna、Paolo Quadrelli
DOI:10.1002/chem.201503062
日期:2015.11.9
derivatives have the geometrical features to be used as β‐turn inducers. Four different stereoisomers were prepared and spectroscopically characterized (MD calculations, NMR‐titration and VT‐NMR experiments). Temperature coefficients in DMSO are indicative for the existence of an intramolecular hydrogen bond. Chirooptical properties revealed a β‐turn arrangement of all the synthesized compounds, where,
Probing Competitive and Co-operative Hydroxyl and Ammonium Hydrogen-Bonding Directed Epoxidations
作者:Marta Brambilla、Méabh B. Brennan、Kristína Csatayová、Stephen G. Davies、Ai M. Fletcher、Alice M. R. Kennett、James A. Lee、Paul M. Roberts、Angela J. Russell、James E. Thomson
DOI:10.1021/acs.joc.7b01774
日期:2017.10.6
hydroxyl group results in direction of the epoxidation to the syn face. In cases where the two potential directing groups can promote epoxidation on the same face of the ring scaffold, an enhancement of epoxidation diastereoselectivity was not observed, while introduction of a second, allylic heteroatom to the substrate results in diminishment of the rate of epoxidation in all cases. Presumably, reduction
Diels-Alder (HDA) and enereactions. Methods: Acylnitroso intermediates were readily obtained by hydrogen peroxide oxidation of hydroxamic acids catalyzed by Cu(I)-, Ir(I)- or Ru(II)-complexes and easily reacted with symmetric and asymmetric conjugated dienes beside their reaction with different alkenes which converted to biological active products. Results: The resulted acylnitroso intermediates were efficiently
Tetrabutylammonium decatungstate (TBADT) promoted the oxidation of hydroxamicacids to nitrosocarbonylintermediates. The reaction took place under aerobic conditions upon irradiation with solar light. The thus generated nitrosocarbonyls were efficiently trapped with reactive dienes to afford the corresponding Hetero Diels‐Alder (HDA) cycloadducts in good yields.