Two new efficient preparations of enantiopure 2,2′-dihydroxy-6,6′-dimethoxy-1,1′-biphenyl
摘要:
Two new useful methods for the preparation of diol 1 starting from available compounds are described. Separation of the two enantiomers entails resolution of racemic diol 1 via the corresponding diastereomeric N-methylated phosphorothioamidates. Their separation by recrystallization followed by reduction afforded diol (aS)-1 and (aR)-1 in 100% and 72% ee, respectively. (C) 1997 Elsevier Science Ltd.
Preparation of enantiomerically pure 1,1'-binaphthalene-2,2'-diol and 1,1'-binaphthalene-2,2'-dithiol
摘要:
A practical preparation of enantiomerically pure 1,1'-binaphthalene-2,2'-diol (1) and 1,1'-binaphthalene-2,2'-dithiol (2) is reported. Enantiopure 2 is obtained from enantiopure 1 via Newman-Kwart rearrangement of the thiocarbamoyl derivative 5 under controlled reaction conditions. The enantiopure starting diol 1 was obtained by a simple and inexpensive method engaging condensation of thiophosphoryl chloride and (S)-(-)-alpha-methylbenzylamine in pyridine and reaction of the resulting phosphoramidate a with racemic binaphthol 1 to give quantitatively a 1:1 mixture of diastereoisomers 4 that were cleanly separated by a single recrystallization from a chloroform-ethanol mixture in very high yield. The procedures can be scaled up easily.
The preparation and resolution of the title conformationally stable biphenyl 9 has been performed in high chemical yield starting from eugenol 1. Enantiopure biphenyls (aR)-(+)-9 and (aS)-(−)-9 were achieved, respectively, by resolution of the corresponding menthylcarbonate diastereomer and subsequent reduction. Absoluteconfiguration and specific rotation were correlated by X-ray analysis of the crystal
A practical route to prepare dithioether, thiophene and thiophene S-dioxide derivatives of 2.2 ' ,3,3 ' -tetramethoxy-1,1 ' -biphenyl 1 is described. Resolution of 6,6 ' -bis(methylithio)-3.3 ' -dimethoxy-[1,1 ' -biphenyl]-2.2 ' -diol 15 was achieved and its absolute configuration was assigned by X-ray analysis of the corresponding phosphorothioamidate diastereomer 18. (C) 2001 Elsevier Science Ltd. All rights reserved.
Preparation of enantiomerically pure 1,1'-binaphthalene-2,2'-diol and 1,1'-binaphthalene-2,2'-dithiol
作者:Davide Fabbri、Giovanna Delogu、Ottorino De Lucchi
DOI:10.1021/jo00059a025
日期:1993.3
A practical preparation of enantiomerically pure 1,1'-binaphthalene-2,2'-diol (1) and 1,1'-binaphthalene-2,2'-dithiol (2) is reported. Enantiopure 2 is obtained from enantiopure 1 via Newman-Kwart rearrangement of the thiocarbamoyl derivative 5 under controlled reaction conditions. The enantiopure starting diol 1 was obtained by a simple and inexpensive method engaging condensation of thiophosphoryl chloride and (S)-(-)-alpha-methylbenzylamine in pyridine and reaction of the resulting phosphoramidate a with racemic binaphthol 1 to give quantitatively a 1:1 mixture of diastereoisomers 4 that were cleanly separated by a single recrystallization from a chloroform-ethanol mixture in very high yield. The procedures can be scaled up easily.
Chiral nonracemic C2-symmetry biphenyls by desymmetrization of 6,6′,2,2′-tetramethoxy-1,1′-biphenyl
Regioselective bromination of the title biphenyl 1 at the 3 and 3' positions and simultaneous desymmetrization of the biphenyl has been achieved. Metal-halide exchange at the 3,3' positions facilitated the introduction of functional groups in good yield. Regioselective reduction was obtained by using (CH3)(3)SiI, L-Selectride and HI according to the functional groups on the biphenyls. Resolution of 6,6',2,2'-tetramethoxy-3,3'-dimethyl-1,1'-biphenyl 3 was achieved by its conversion to the corresponding phosphorothioamidate diastereomers of the (S)-(-)-alpha -methylbenzylamine. The absolute configuration of (M)-(+)-3 was confirmed by X-ray analysis of the corresponding diastereomer. (C) 2000 Elsevier Science Ltd. All rights reserved.
New axially chiral sulfur compounds: Synthesis and conformational stability of enantiopure 4,4′-biphenanthrene-3,3′-dithiol and related atropisomeric derivatives
作者:Antonio Dore、Davide Fabbri、Serafino Gladiali、Giovanni Valle
DOI:10.1016/0957-4166(95)00074-y
日期:1995.3
Enantiopure (R)- and (S)-4,4'-biphenanthrene-3,3'-dithiol la has been prepared for the first time through a synthetic procedure involving in the key step a stereoconservative Newman-Kwart thermorearrangement of the bis-N,N-dimethylthiocarbamoyl ester of(R)- and (S)-biphenanthrol 2b, respectively. The atropisomeric conformations of la are not interconverted even at temperatures as high as 285 degrees C, whereas the related biphenanthrothiophene 3 is completely racemized in a few minutes at 250 degrees C. The axially chiral backbone of la has been incorporated in a set of novel C-2 symmetry sulfur reagents suitable for a variety of stereoselective reactions.