Synthesis of β-oxo carbonyl and thiocarbonyl compounds via basic sulfur abstraction
作者:Saúl Silva、Christopher D. Maycock
DOI:10.1016/j.tet.2019.130552
日期:2019.10
suitable thioesters represents a mild method for the formation of carbon-carbon bonds and the formation of 1,3-dicarbonyl compounds. A study of the scope and limitations of this reaction for the synthesis of these or mixed 1,3-carbonyl/thiocarbonyl compounds by a base promoted sulfur abstraction rearrangement is described. These reactions were typically very clean and the products were obtained in good
Kinetically distinct triplets in the photorearrangement of 2-phenylcyclohexanone to cis- and trans-6-phenyl-5-hexenals
作者:Peter J. Wagner、Thomas J. Stratton
DOI:10.1016/s0040-4020(01)92379-8
日期:——
an almost concerted out-of-plane cleavage which forms a 1,6-biradical in the perfect geometry for disproportionation to trans-enal.The precursor to cis-enal may be a minor rotamer of 1 which is forced by nonbonded interactions into a cleavage mode which twists the biradical into a geometry suitable for at least partial formation of cis-enal. In both cases biradicals must be very short-lived and not
Novel triazolocycloalkylhydrothiadiazines and their preparation, which are useful as antisecretory agents, central nervous system stimulants, and central nervous system depressants, are disclosed.
Axial equatorial populations were determined for (E)-2-X-cyclohexanone oximes and O-methyl oxime ethers in chloroform by the Eliel method [X = F, Cl, Br, OCH3, N(CH3)(2), SCH3]. A novel approach is presented, which uses H-1 NMR data from the protons bonded to C-6. The conformational proportions were also obtained from the C-4 chemical shifts, the Z-isomer spectral parameters being taken as reference for calculation. For both series, all substituents adopt preferentially the axial conformation (86-96%), but the O-methyl oxime ethers present an enhanced axial population compared with the corresponding oximes, owing to the accepted occurrence of a pi(C=NOH)/sigma(CX)* stabilizing interaction. Copyright (C) 2000 John Wiley & Sons, Ltd.