摘要:
A process for the manufacture of 4,4-disubstituted 5-methylene-1,3-dioxolan-2-ones ("cyclocarbonates") of the formula: ##STR1## wherein R.sup.1 and R.sup.2 each independently signify a saturated or olefinically-unsaturated aliphatic group or an aromatic group, or R.sup.1 and R.sup.2 together form tetra- or pentamethylene, by reacting a corresponding 3,3-disubstituted prop-1-yn-3-ol of the formula HC.tbd.C--C(R.sup.1)(R.sup.2)--OH (II) with carbon dioxide in the presence of a quaternary ammonium or phosphonium salt as the catalyst comprises using a silver salt as a further catalyst. An alkali metal or quaternary ammonium or phosphonium salt of a carboxylic acid can also be used to increase the catalytic performance of the silver salt catalyst. Moreover, the addition of triphenylphosphine serves to accelerate the reaction to some extent. The silver salts catalyze this process significantly better than the previously utilized copper salts. Advantageously, the process uses much smaller amounts of catalyst, significantly shortens reaction times, and mandates less drastic reaction conditions. Cyclocarbonates produced by this process are valuable intermediates for the production of polymerizates and other useful substances, such as dyestuffs and carotenoids.
摘要:
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## or --CH.sub.2 --CH.dbd.NR.sup.2 in which R.sup.2 and R.sup.3 represent 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, inter alia, natural vitamin E and natural vitamin K.sub.1.
摘要:
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.
摘要:
Compounds of the formula ##STR1## wherein R.sup.1 -R.sup.4 is hydrogen or chlorine, R.sup.5 is --COOMe or --SO.sub.3 Me, Me is an alkali metal cation and X is oxygen, sulfur or selenium,photosensitizers for the conversion of tachysterol into previtamin D are described. The tachysterol content in mixtures of previtamin D and tachysterol can be greatly reduced by UV-irradiation in the presence of such photosensitizers.
摘要:
Novel chiral phosphorus compounds of the general formula ##STR1## wherein R signifies substituted or unsubstituted phenyl, R.sup.1 and R.sup.2, which can be the same or different, signify hydrogen, lower alkyl, lower alkoxy, di-lower alkylamino or protected hydroxymethyl or R.sup.1 and R.sup.2 together signify the group ##STR2## in which m represents a number 3 to 5, R.sup.4 represents lower alkyl, substituted or unsubstituted phenyl or benzyl and R.sup.5 represents lower alkyl or both R.sup.5 's together represent lower alkylene, R.sup.3 signifies methyl, lower alkoxy, di-lower alkylamino or fluorine and n signifies the number 0, 1, 2 or 3, are described.The compounds of formula I are useful in the form of complexes with a metal of Group VIII as catalysts for asymmetric hydrogenations and enantioselective hydrogen displacements in prochiral allylic systems.
摘要:
Compounds of the formula ##STR1## wherein R.sup.1 -R.sup.4 is hydrogen or chlorine, R.sup.5 is --COOMe or --SO.sub.3 Me, Me is an alkali metal cation and X is oxygen, sulfur or selenium, photosensitizers for the conversion of tachysterol into previtamin D are described. The tachysterol content in mixtures of previtamin D and tachysterol can be greatly reduced by visible light irradiation in the presence of such photosensitizers.