Pyrrolo[1,2-d]triazines-1,2,4. II. Etude des pyrrolo[1,2-d]triazinones-1 et -4

The synthesis of 1,2-dihydro-1-oxopyrrolo[1,2-d]-1,2,4-triazines was achieved by rearrangement of 2-pyrrolyloxadiazoles under alkaline conditions or by cyclisation of pyrrole N-ethoxymethylidene hydrazides. The cyclisation of the N-carbethoxy hydrazone of the pyrrole-2-carboxaldehyde gave the 3,4-dihydro-4-oxopyrrolo[1,2-d]-1,2,4-triazine. Electrophilic substitution reactions of the 1- and 4-pyrrolotriazinones were made either on the lactam nitrogen with methyl sulphate, benzyl chloride and monochloroacetic acid or on the pyrrole ring with bromine and nitric acid. The structure of the derivatives was determined by ¹H nmr.     

Pyrazolo[1,5-d]triazines-1,2,4. I. Dérivés pyrazoliques

Pyrazole hydrazides and hydrazines were synthesized from pyrazole-5-carboxylic acid, 4-bromopyrazole-5-carboxylic acid and pyrazole-5-carboxaldehyde. The 5-pyrazolyloxadiazoles and 5-pyrazolylthiadiazoles were obtained by cyclising the pyrazole hydrazides with phosphorus oxychloride and tetraphosphorus decasulphide. Cyclisations in 1,2-dihydro-1-oxo- (or l-thioxo)pyrazolo[1,5-d]-1,2,4-triazines were eventually observed. The structures were assignated by nmr.     

2‐(6‐Bromopyridin‐3‐yl)‐4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolane and (6‐bromopyridin‐3‐yl)boronic acid,new bifunctional building blocks for combinatorial chemistry

The first comparative study between two new heterocyclic boron derivatives, viz. a (6‐bromo­pyridin‐3‐yl)­boronic ester, C₁₁H₁₅BBrNO₂, and (6‐bromo­pyridin‐3‐yl)­boronic acid, C₅H₅BBrNO₂, shows a small but not significant difference in their C—B bond lengths, which cannot explain the experimentally observed difference in their stabilities. The crystal packing of the boronic ester consists principally of van der Waals interactions, while the boronic acid mol­ecules interact in their crystal through hydrogen bonds.     

Synthesis of New Avenalumic Carboxamide Derivatives in the Ferulic Series

A seven-step synthesis of (2E,4E)-5-[4-hydroxy-3-methoxyphenyl]penta-2,4-dienoic acid from ferulic acid was developed. The use of a natural by-product found in rice bran as a raw material provided the ferulic acid vinylogous in an overall high yield. This compound will be useful for the preparation of a wide variety of avenalumic carboxamide derivatives.     

Preparation and characterization of MgB2 superconductor

The MgB₂ superconductor, synthesized using solid-state and liquid-phase sintering methods, have been characterized for various properties. The upper critical field, irreversibility line and critical current density have been determined using magnetization data. The current-voltage characteristics recorded under an applied magnetic field revealed the existence of vortex glass transition. The surface analysis using X-ray photoelectron spectroscopy shows that MgB₂ is sensitive to atmospheric degradation.     

New fused pyrazines. Synthesis of pyrido[3′,2′:4,5]‐thieno[2,3‐e]pyrrolo[1,2‐a]pyrazine derivatives

The synthesis of the title compounds was achieved using the key intermediate ethyl 4,6‐dimethyl‐3‐(pyrrol‐1‐yl)thieno[2,3‐b]pyridine‐2‐ carboxylate 2. This latter compound was obtained via the interaction of the thienopyridine amino ester 1 with 2,5 dimethoxytetrahydrofuran in acidic medium.