Determination of the electrophilic reactivities of 1,1,3-triarylallyl cations
作者:Herbert Mayr、Claudia Fichtner、Armin R. Ofial
DOI:10.1039/b203554e
日期:——
The 1,1,3-triphenylallyl cation and its p-methoxy and p-dimethylamino substituted derivatives have been generated in dichloromethane solution or as stable salts. Allylsilanes, allylstannanes, silylated enol ethers and ketene acetals, as well as enamines attack the sterically less hindered 3-position of the allyl cation as derived from the structures of the reaction products. Kinetic investigations of these reactions revealed that they follow the equation log k(20 °C) =
s(N
+
E), which allows one to derive the electrophilicity parameters E of Ph2CCH–CH+Ph (E
=
+0.98 ± 0.20), (p-MeOC6H4)2CCH–CH+Ph (E
=
−2.67 ± 0.30), (p-Me2NC6H4)2CCH–CH+Ph (E
=
−8.97 ±
0.32) and (p-Me2NC6H4)2CCH–CH+(p-Me2NC6H4) (E
=
−9.84 ± 0.21).
coefficient plots indicate that steric interactions between the chalcones and the target are of major importance for the potencies of the compounds. A comparison of the coefficient plots for the antileishmanial effect and the lymphocyte-suppressing activity discloses significant differences which should make it possible to design chalcones having a high antileishmanial activity without suppressing the
<i>Michael</i>Reactions of α-Unsubstituted Trisubstituted 1<i>H</i>-Pyrroles
作者:Rainer Lüönd、Reinhard Neier
DOI:10.1002/hlca.19910740111
日期:1991.1.30
To obtain stable derivatives of α-unsubstituted pyrroles, the reaction of the test pyrrole 9 with a series of chalcones 14a–h were studied. Michael adducts 16b–h could be isolated. In order to synthesize coloured derivatives, the reaction of different pyrroles 9, 21, 23, and 25 with diphenylpropynone 19 was investigated. In these cases, too, Michael-addition products were formed. The intense absorption
A curable composition comprising (a) a curable polyimide soluble in organic solvents and (b) a polymerization initiator as essential components, said polyimide consisting of recurring units represented by the formula
wherein, each of X, X1, X2, X3 and X4 is a tetravalent carbocyclic or heterocyclic residue, each of Y1, Y2 and Y3 is a divalent carbocyclic or heterocyclic residue, at least one of Z1 and Z2 is a residue having a reactive carbon-carbon double bond, and each of I, m, and n is an integer of 0 or larger.
A precursor of a low thermal stress polyimide and a photopolymerizable composition containing a polyimide precursor
申请人:Asahi Kasei Kogyo Kabushiki Kaisha
公开号:EP0355927A2
公开(公告)日:1990-02-28
Disclosed is a polyimide precursor comprising a specific polyamic acid ester, polyamic amide or polyamic acid salt structure derived from a tetracarboxylic acid compound and a diamine compound, which can be converted by heating to a polyimide having low thermal stress. By blending a specific form of this novel polyimide precursor which has an ethylenic double bond, with a photopolymerization initiator, an excellent photopolymerizable composition can be obtained. Not only this precursor but also the crosslinked precursor obtained by the photopolymerization of the photopolymerizable composition can be converted by heating to a polyimide resin which has low thermal expansion coefficient, high heat resistance, excellent mechanical properties and satisfactory adhesion to a substrate. Hence, the precursor and the photopolymerizable composition can advantageously be utilized in the production of electrical and electronic components.