Pyrimidine reactions. Part XX. Thermal rearrangement of 5-(p-substituted phenyl)-2(and 4)-methoxypyrimidines

Abstract

2(and 4)-Methoxy-5-phenylpyrimidine and some p-substituted derivatives are rearranged by heating in triethylamine to give the corresponding N-methyl-2(or 4)-oxopyrirnidines. The log kl values for rearrangement of the 2-methoxypyrimidines show a rectilinear relationship to the known u values for p-substituted phenyl groups, save when such values are highly negative. 4-Methoxy-5-phenylpyrimidine and its p-nitro-derivative rearrange more rapidly than their respective 2-methoxy-isomers: in addition, each gives a mixture of N-1 and N-3 methylated products in which the latter predominates. These facts are consistent with the recently proposed intermolecular and ionic nature of such rearrangements. Some of the intermediate 2-hydroxy-5-phenylpyrimidines and their N-methyl derivatives are made by a novel modification of the principal pyrimidine synthesis, namely condensation of urea or N-methylurea with 3-irnino-2-phenylpropionaldehyde or a derivative. N.m.r. and U.V. spectra are used to follow rearrangements and to confirm structures.

Design of Liquid Crystals with “de Vries-like” Properties: Frustration between SmA- and SmC-Promoting Elements

“…The mesogens 2( n ) were derived from commercially available 2-(4-hydroxyphenyl)-5-pyrimidinol ( 4 ) via sequential Mitsunobu reactions with the appropriate chloro-terminated alcohols to give 5( n ) , and with 11-(1,1,1,3,3,5,5-heptamethyltrisiloxanyl)-undecanol, as shown in Scheme (see Supporting Information for details). The mesogens 3( n ) were derived from 2-chloro-5-(4-methoxyphenyl)pyrimidine ( 6 ) by a nucleophilic aromatic substitution reaction with the appropriate sodium alkoxides to give 7( n ) , followed by selective demethylation using NaSEt to give 8( n ) and then alkylation via a Mitsunobu reaction with 11-(1,1,1,3,3,5,5-heptamethyltrisiloxanyl)undecanol to give 3( n ) .…”

Design of Liquid Crystals with “de Vries-Like” Properties: Organosiloxane Mesogen with a 5-Phenylpyrimidine Core

“…22 In this Communication, we report the synthesis and charac-terization of this new material, which is comparable to the best "de Vries-like" liquid crystals reported heretofore. 6,7 Compound 2 was obtained by conversion of 2-chloro-5-(4methoxyphenyl)pyrimidine 23 to 5-(4-methoxyphenyl)-2-(1-octyloxy)pyrimidine by a nucleophilic aromatic substitution reaction, followed by selective demethylation using NaSEt and alkylation via a Mitsunobu reaction with 11-(1,1,1,3,3,5,5-heptamethyltrisiloxanyl)undecanol (Supporting Information). The mesophases formed by compound 2 were characterized by polarized optical microscopy (POM) and differential scanning calorimetry (DSC).…”

Ultraviolet spectrometry

“…The site of protonation in isomeric aminoquinolines was determined from shifts in electronic spectra (810). Ultraviolet spectrophotometry was used to follow rearrangements and confirm structures in a study of the thermal rearrangement of substituted methoxypyrimidines (50). The spectra of iodide in aqueous gels were used as an indication of the structure of the water in the gel (45).…”