Process for the manufacture of optically active compounds
申请人:Hoffmann-La Roche Inc.
公开号:US04902818A1
公开(公告)日:1990-02-20
The manufacture of optically active bifunctional compounds of the general formula ##STR1## wherein R represents protected hydroxymethyl, protected formyl or alkoxycarbonyl and R.sup.1 represents a group of the formula ##STR2## in which R.sup.2 and R.sup.3 represents lower alkyl or cycloalkyl or R.sup.2 and R.sup.3 together with the nitrogen atom represent a heterocyclic ring, by isomerizing compounds of the general formula ##STR3## wherein R, R.sup.2 and R.sup.3 have the above significance and R.sup.3 can additionally signify hydrogen, is described. The compounds of formula I are potential intermediates in the manufacture of, interalia, natural vitamin E and natural vitamin K.sub.1.
Synthesis of Optically Active Bifunctional Isoprenoid Building Blocks by Rhodium(I)-Catalyzed Asymmetric Allylamine to Enamine Isomerization
作者:Rudolf Schmid、Hans-J�rgen Hansen
DOI:10.1002/hlca.19900730516
日期:1990.8.8
The application of the known asymmetric allylamine to enamine isomerization methodology to bifunctional C5-isoprenoid allylic amines of types IId and IIe (Scheme 1) is described. It is shown that a number of such substrates can be isomerized with enantioselectivities of > 90% ee. using cationie Rh1 complexes containing (6. 6′-dimethylbiphenyl′2, 2′-diyl)bis(dipheny phosphine) (BIPHEMP; 9) as asymmetry-inducing
Process for the preparation of carboxylic acid esters of
申请人:BASF Aktiengesellschaft
公开号:US04301084A1
公开(公告)日:1981-11-17
In a process for the preparation of a carboxylic acid ester of .beta.-formyl-crotyl alcohol by rearrangement of the corresponding carboxylic acid ester of 2-formyl-2-hydroxy-but-3-ene or of an acetal or acylate thereof in the presence of copper or a copper compound, followed, where relevant, by hydrolytic cleavage of the acetal or acylate, more especially in the preparation of 4,4-dimethoxy-3-methyl-crotyl acetate, the yield is improved by carrying out the rearrangement in the presence of copper (I) chloride as the catalyst and ensuring that low-boiling by-products formed during the rearrangement are removed. The products are of great importance as starting materials for an industrial synthesis of vitamin A and its derivatives.