Synthesis and reactivity of some β - substituted alkylphosphonates

The ability of the β-trimethylammonioethylphosphonic acid dianion to undergo fragmentation in alkaline conditions to produce trimethylamine, ethylene and metaphosphate was investigated. The results obtained were to give an indication of the susceptibility of (C6H3Cl2)OCH2CH2N+R2CH2CH2P(OR')O2- to analogous fragmentation to release 2-(3,4-dichlorophenoxy)ethyldialkylamine and ethylene, both well documented plant growth regulating hormones. Since the trimethylammonioethyl-substituted species was found to be stable to fragmentation, studies were embarked upon to convert this molecule into one which would react as required. Attempts at its synthesis were made by various approaches. Attempts at the synthesis of diethyl 2-iodopentylphosphonate and diethyl 2-bromopentylphosphonate by various means are described, but no satisfactory syntheses have been achieved, since once again the dehydrohalogenation product predominates. During an attempted synthesis of diethyl 2-iodopentylphosphonate by reaction of diethyl 2-chloropentylphosphonate with NaI, an unusual interaction between the sodium cation and the substrate in acetone solution was discovered. Evidence gleaned from 1H, 13C and 31P nmr experiments points to the formation of a loose complex between the phosphonate part of the substrate and Na+. This phenomenon is also observed when other salts such as CaI2, KSCN and NaClO4 are present in solution