Iodine-induced cyclization reaction of O,O-dialkyl 4-pentenylphosphonates

Abstract

The stereoselective synthesis of cts-2-alkoxy-2-oxo-6-(iodomethyl)-l,2-oxaphosphorinanes is achieved by the treatment of , -dialkyl 4-pentenylphosphonates with iodine. The intermediates involved in iodine-induced cyclization reactions of ¿-unsaturated phosphonates could be observed directly by 31P NMR at 37 °C. The effects of the iodine concentration and solvents on the cyclization reaction were investigated. In chloroform, there were two intermediates, the major one being (4,5-diiodopentyl)phosphonate; the other one could be a cyclic alkyl trialkoxyphosphonium ion. In benzene and cyclohexane, in addition to these two intermediates, there was at

Substituent effects on the pyrolysis of .alpha.-chloro-o-xylenes

“…Unreacted starting materials were determined by GLC. 6 The reaction conversion was defined as the amount of -chloro-o-xylene passed through the reactor minus the recovered starting material.…”

“…The results in Table II show that an electron-donating moiety para to the chloremethylene group enhances the reactivity more than its meta isomer. To react a mixture of 2-methyl-4-carbomethoxybenzyl chloride (6) and 2-methyl-5-carbomethoxybenzyl chloride (4) shows that an electron-withdrawing substituent retards the reaction more when it is para to the chloromethylene group.…”

“…The differential equation for the formation of acetic acid, dA/dt = [S]fe! + [RS]fe2 (6) can be written as (by using eq 1 and 2)…”

A facile method to construct cyclic α,α-difluoromethylenephosphonate—A novel cyclic phosphate mimic

“…According to the results obtained with the reaction of O,Odialkyl-v-alkenylphosphonate and Br 2 by Zhao and Yan [11] and Shibuya and co-workers [12], we considered that due to the relative low nucleophilicity of the oxygen atom of phosphonyl group as well as to some difficulty in the collapse of the O-Et bond with the assistance of bromine anion in the presumed bromonium intermediate A (Scheme 4), intramolecular attack (path 1) may be highly suppressed by its competitive intermolecular reaction (path 2). Therefore, our attention was next turned to the synthesis of ballenic phosphonic acid monoesters 4 which might facilitate intramolecular cyclization by readily losing proton in the cyclization key step, and hydrolysis of 1 was investigated.…”

Structure of 6-(iodomethyl)-2-oxo-2-phenoxy-1,2-oxaphosphorinane

“…The synthesis of the phosphonate ester was accomplished by a stereospecific cyclization of phenyl isopropyl-4-pentenylphosphonate induced by iodine (Zhao &Yan, 1985) followed by conversion of the iodomethyl derivative to the desired compound.…”