<sup>13</sup>C nuclear magnetic resonance spectra of methoxycyclohexane derivatives. Rotamer populations about C–OMe bonds as indicated by<sup>13</sup>C chemical shifts of methoxy- and ring-carbons and<sup>3</sup>J<sub>C,H</sub>coupling constants
作者:Alan H. Haines、Mohammad Seyedi Shandiz
DOI:10.1039/p19810001671
日期:——
Methoxy 13C chemicalshifts in methoxycyclohexanederivatives may be rationalized in terms of rotamerpopulationsabout the C–OMe bond and δ1-effects caused by steric interaction of the methoxy-group with substituents at the neighbouring 2- and 6-positions. Information on rotamerpopulations is obtained also from the 13C chemicalshifts of C-2 and C-6, and from the three-bond coupling between the proton
Methyl-triisopropoxy-titanium, a highly selective nucleophilic methylating reagent. Preliminary Communication
作者:Beat Weidmann、Dieter Seebach
DOI:10.1002/hlca.19800630839
日期:1980.12.10
Replacement of lithium or magnesium by titanium can furnish nucleophilic organometallic reagents of high selectivity as exemplified by the title compound 1 (see Tables 1–3).
Highly Efficient Conversion of Alcohols to Isocyanides
作者:Yoshikazu Kitano、Kazuhiro Chiba、Masahiro Tada
DOI:10.1055/s-2001-11423
日期:——
Treatment of tertiary alcohols with silver salts (AgClO4, AgBF4, or AgOTf) and trimethylsilyl cyanide (TMSCN), followed by hydrolysis, directly affords excellent yields of corresponding isocyanides. This reaction proceeds selectively with tertiary alcohols in the presence of primary and secondary alcohols.
selectivity. trans-Oxazolidinones were prepared from acyclic secondary N-mesyloxycarbamates using Rh2(oct)4. The selectivity was reverted with a cytoxazone N-mesyloxycarbamate precursor using large chiralrhodium(II) carboxylate complexes, affording the corresponding cis-oxazolidinone. This orthogonal selectivity was used to achieve the formal synthesis of (−)-cytoxazone.
Ligand effects in selective carbonyl addition reactions of organomanganese and cerium reagents
作者:Manfred T. Reetz、Helmut Haning、Stephan Stanchev
DOI:10.1016/s0040-4039(00)60907-3
日期:1992.11
Transmetalation of organolithium reagents RLi (R = CH3, n-Bu) with manganese pivalate produces reagents of the type RMnOC(O)tBu which react stereoselectively with substituted cyclohexanones to afford the axial alcohols preferentially. These reagents as well as cerium ate complexes RCe(OiPr)3MgX react aldehyde-selectively in the presence of ketone functionality.
有机锂试剂RLi(R = CH 3,n -Bu)与新戊酸锰铁的金属过渡生成类型为RMnOC(O)t Bu的试剂,该试剂与取代的环己酮发生立体选择反应,从而优先提供轴向醇。这些试剂以及铈酸盐络合物RCe(O i Pr)3 MgX在酮官能团存在下选择性地与醛发生反应。