The reactivity of organophosphorus compounds. Part XXVIII. Fast, neighbouring group-induced rearrangement during alkaline hydrolysis of α-hydroxyimino-p-nitrobenzyl phosphates, phosphonates, and phosphinates

Synthesis and Properties of Phosphetanes

“…Ring strain also accelerates the alkaline hydrolysis of phosphinate esters (10 2 times faster than acyclic analogues). 151,152 Note: unlike the nucleophilic substitutions on tetravalent derivatives above, substitutions on trivalent P-chlorophosphetanes with amines, alcohols, or organolithium reagents take place as expected, with inversion of the phosphorus configuration. 13,87,134,153 In a few cases only, when the entering group is rather mobile (alkoxy and amino groups), the first-formed product can be isomerized by subsequent substitution reactions.…”

“…This reflects relief of ring strain in the intermediate phosphorane. Ring strain also accelerates the alkaline hydrolysis of phosphinate esters (10 2 times faster than acyclic analogues). , …”

Nucleophilic addition and subsequent oxime-assisted ester hydrolysis of diethyl .beta.-ketopropylphosphonate

“…A similar behavior was observed for the ester hydrolysis of alkyl -hydroxyimino-p -nitrobenzyl alkylphosphonates in almost the same pH region. 3 In fact, the rate constant for this system (1.2 X 10-3 s-1) is almost identical to that for SOX even though the mechanism for monoester formation is probably different in the two cases, i.e., via N-0 bond cleavage for the hydroxyimino compound. This similarity in rates could mean that the rate-determining step in the ester hydrolysis is the intramolecular nucleophilic addition of the oxime oxygen to phosphorus.…”

“…Classically, isoxazoles are made by reaction of 1,3-dicarbonyl compounds (1) with hydroxylamine followed by dehydrative cyclization of an intermediate monooxime. 3 When R and R" in 1 are not the same, two isomeric isoxazoles (2) are possible. Both are obtained when R and R" are similar, a complication which usually leads to major separation prob-…”

“…This assistance probably involves addition to phosphorus to form a pentacovalent intermediate similar to that suggested previously to explain the intramolecular assistance to phosphonate ester hydrolysis caused by an amide2 and an oxime. 3 For the latter, the mechanism differs from Scheme I in that monoester formation occurs via O-N rather than O-P bond scission. For the former, the rate of amide assisted hydrolysis becomes appreciable only in highly acidic solutions and, consequently, amide assistance appears to be less effective than oxime assistance, which induces hydrolysis in neutral solution.…”