Thioindigo precursor: control of polymorph of thioindigo

2,2′-Bi[-3(2H)-thiophenon]ylidene with two bicyclo[2.2.2]-octadiene moieties was quantitatively converted to thioindigo by the retro-Diels-Alder reaction. The thioindigo solid obtained from the precursor had the P2₁/c structure which was different from the commercial thioindigo samples (P2₁/n).     

Enantio- and diastereoselective total synthesis of EI-1941-1, -2, and -3, inhibitors of interleukin-1beta converting enzyme, and biological properties of their derivatives

[reaction: see text] The first asymmetric total synthesis of EI-1941-1, -2, and -3, inhibitors of the interleukin-1beta converting enzyme (ICE), has been accomplished, starting from a chiral epoxy iodoquinone 11, a key intermediate in our total synthesis of epoxyquinols A and B. Despite a failure to synthesize the inhibitors by our postulated biosynthetic route, we were able to diastereoselectively synthesize them via an intramolecular carboxypalladation with the key steps being a 6-endo cyclization mode followed by beta-hydride elimination. The investigation of the biological properties of EI-1941-1, -2, and -3 and their derivatives disclosed them to be potent and effective ICE inhibitors with less cytotoxicity than EI-1941-1 and -2 in a cultured cell system.     

Polymerization of isocyanates. V. Thermal degradation of polyisocyanates

Thermal degradation of polyisocyanates was investigated. The only degradation products were monomer and trimer. The main product was trimer for most aliphatic polymers, and monomer for aromatic polymers. Poly(cyclohexyl isocyanate) gave only its monomer on account of steric requirements. The apparent activation energy was calculated for aromatic polymers by using TGA and DTA curves.     

Spontaneous reactions of electron‐accepting substituted quinodimethane with substituted styrenes: Inductive and steric effects on the formation of a zwitterionic intermediate

Spontaneous reactions of an electron‐accepting substituted quinodimethane, 1‐(2,2‐dimethyl‐1,3‐dioxane‐4,6‐dione‐5‐ylidene)‐4‐(dicyanomethylene)‐2,5‐cyclohexadiene, with p‐substituted, α‐substituted, and β‐substituted styrenes were investigated. When p‐substituted styrenes were used as comonomers, no spontaneous reactions took place for styrenes with an electron‐accepting p substituent such as COOMe and CN groups, and both terpolymers and cycloadducts were formed for the other p‐substituted styrenes. When α‐substituted and β‐substituted styrenes were used as comonomers, no reactions occurred for α‐ and β‐substituted styrenes with a bulky phenyl group, and spontaneous reactions took place for those with a smaller methyl group. The reaction products were an alternating copolymer for α‐substituted styrene and both terpolymers and 5‐ethylidene‐2,5‐dimethyl‐1,3‐dioxane‐4,6‐dione for β‐substituted styrenes. The position of the methyl group in the styrenes significantly affected the product formation. This behavior in the spontaneous reactions was discussed on the basis of the ability of formation of the zwitterionic tetramethylene intermediate and its conformation, determined by polar and steric effects of the substituents in the substituted styrenes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5195–5206, 2005     

Functional monomers and polymers. XCV. Photochemical reactions on synthetic polymers having pendant thymine bases in polymethyl methacrylate film

The photodimerization reaction of synthetic polymers which contain thymine bases was studied in polymethyl methacrylate film. The quantum efficiency for the photodimerization of the thymine bases of polyacrylate and polymethacrylate, fixed in the polymethyl methacrylate film was measured. The value of the film was higher than those measured in solution.     

Novel thermostable polymers from bis-o-aminophenylbenzimidazoles and aromatic tetracarboxylic dianhydrides

Novel aromatic hetero polymers, polybenzoylenebenzimidazoquinazolines, were prepared. These polymers were synthesized by the polymerization of bis-o-aminophenylbenzimidazoles with aromatic tetracarboxylic dianhydrides in organic solvents, followed by cyclocondensation of the polyamic acids in polyphosphoric acid. In the resulting polymers the o-phenylenediamine component behaved trifuntionally and the connecting groups were tricyclic fused rings that contained seven-membered rings. These polymers some of which has a ladder-type structure, exhibited excellent thermal properties.