Synthesis of new enantiomerically pure monoketals of p-benzoquinone with C2-symmetry
摘要:
Several new monoketals of p-benzoquinone with the structure of 1,3-dioxaspiro[4.5]deca-6,9-dien-8-one have been synthesised in enantiopure form by the straightforward reaction of the quinone with secondary C-2-symmetric 1,2-diols. The preparation of two new enantiopure C-2-1,2-glycolsis also reported. (C) 1999 Elsevier Science Ltd. All rights reserved.
Pinacol Coupling Reaction of β-Halo-α,β-unsaturated Aldehydes Promoted by TiI4
摘要:
[GRAPHICS]The pinacol reaction of beta-halogenated alpha,beta-unsaturated aldehydes was promoted by titanium tetraiodide to give coupling products in good yields with high di-selectivity. Subsequent reduction with H-2/Pd-C gave saturated vic-diols in good yields. Heck coupling reaction enabled the displacement of halogens with vinyl groups without the loss of stereochemical integrities.
Efficient method for the preparation of pinacols derived from aromatic and aliphatic ketones by using low-valent titanium reagents in dichloromethane-pivalonitrile
aldehydes and ketones, including unsymmetrical aliphatic ketones, proceeded smoothly to give the corresponding pinacols in good to high yields under mild conditions by using combination of titanium(II) chloride and zinc or titanium(IV) chloride and zinc in dichloromethane-pivalonitrile. Meso-selective formation of the coupling products was observed in the cases of some aliphatic ketones. The diastereoselectivities
Synthesis of chiral nonracemic diols via nucleophilic opening of (S,S)-1,2,3,4-diepoxybutane
作者:Paul N. Devine、Taeboem Oh
DOI:10.1016/s0040-4039(00)92111-7
日期:1991.2
(S,S)-1,2,3,4-diepoxybutane was synthesized from (R,R)-dimethyl tartrate. Nucleophilic opening of this diepoxybutane gave a convenient method for generating a variety of chiral nonracemic diols.
作者:Helen C. Aspinall、Nicholas Greeves、Carine Valla
DOI:10.1021/ol050256f
日期:2005.5.1
of samarium diiodide (SmI(2)) with tetraglyme catalyzes the intermolecular pinacolcoupling of aromatic or aliphatic aldehydes at loadings of 10 mol % in the presence of Me(2)SiCl(2) and Mg. Diastereoselectivity of up to 95/5 (+/-/meso) has been achieved for aliphatic aldehydes and up to 19/81 (+/-/meso) for aromatic aldehydes. De values of up to 99% have been achieved in intramolecular pinacol coupling
Aromatic aldimines reacted with Sr in the presence of a catalytic amount of iodine to give self-coupling products in good yields, whereas aromatic and aliphatic aldehydes underwent a similar reaction effected by the combined use of Sr and Al(OEt)3.