Phosphoryl to carbonyl migration of amino groups in mixed anhydrides

Abstract

JILL SYMES and TOMA~Z A. MODRO. Can. J. Chem. 64, 1702(1986. Mixed anhydrides derived from carboxylic and amidophosphoric acids, (RO)(Rr2N)P(0)OC(O)R" (I), undergo unimolecular fragmentation yielding carboxyamides, R"C(0)NRf2, and metaphosphate esters, ROPO,. The mechanism of the amino group transfer was studied for substrate l a (1, R = R' = Me; R" = Ph); solvent as well as substituent effects indicate little (if any) charge development in the transition state. The effects of solvents and Lewis acids on the reaction rate and the activation parameters determined for l a can be explained best in terms of stabilizing interactions with either carboxyamide or metaphosphate being formed in the course of reaction. The transfer of a functional group from one acyl center to another was investigated for other anhydride systems and the relative contributions of the fragmentation vs. disproportionation of substrates are discussed.JILL SYMES et TOMASZ A. MODRO. Can. J. Chem. 64, 1702(1986. Les anhydrides mixtes, (RO)(R'2N)P(0)OC(O)R" (I), obtenus a partir d'acides carboxyliques et d'acides amidophosphoriques subissent des fragmentations unimolCculaires conduisant aux carboxyamides, R"C(0)NR'2, et aux esters mCtaphosphates, ROP02. On a CtudiC le mCcanisme de transfert du groupement aminC dans le substrat l a (1, R = R' = Me; R" = Ph); les effets de solvant ainsi que les effets de subatituant indiquent qu'il n'y a que peu (s'il en existe) de dkveloppement de charge dans 1'Ctat de transition. Dans le cas du compost5 l a , on a dCtenninC les effets des solvants et des acides de Lewis sur les vitesses de rkaction et sur les paramiitres d'activation; les meilleures explications pour ces rCsultats sont bastes sur les interactions stabilisantes qui se foment au cours de la rCaction soit avec le carboxyamide ou le mktaphosphate. On a CtudiC le transfert d'un groupement fonctionnel d'un centre acyle a un autre dans d'autres systkmes d'anhydrides et on discute des contributions relatives la fragmentation des substrats par rapport a leur disproportionation.[Traduit par la revue]The ability of a functional group, such as alkyl ester OR, to migrate from one phosphoryl centre to another in a phosphoric anhydride was noticed as early as 1914 (I), when the formation of trialkyl phosphates was found to occur on thermal decomposition of tetraalkyl pyrophosphates. Reorganisation between structural units in an anhydride system was confirmed in later studies (2) on the polyphosphate esters with insecticidal properties. In the case of mixed anhydrides of dialkylphosphoric and carboxylic acids the major reaction is the disproportionation to a pair of symmetrical anhydrides; the reaction has been used (3) as a synthetic route to tetraalkyl pyrophosphates. It was reported, however (3), that when the mixed anhydrides contained a dialkylamide group, a considerable quantity of N,N-dialkylcarboxyamide was also formed, e.g.:In consequence, acyl phosphates can undergo fragmentation . .according to two independent pathways; (i) the (necessarily) bimolecula...

The Case for the Intermediacy of Monomeric Metaphosphate Analogues during Oxidation of H-Phosphonothioate, H-Phosphonodithioate, and H-Phosphonoselenoate Monoesters: Mechanistic and Synthetic Studies

“…An intriguing feature of path B is that it would constitute a new mechanistic pathway in which metaphosphate analogues could be formed. Usually metaphosphates and their analogues are generated from P(V) derivatives bearing a good leaving group and an internal nucleophile as is shown in Scheme . ,,,,, For cyclic phosphorus compounds, Z and X are part of a ring system, and fragmentation to metaphosphates occurs under pyrolytic conditions. , Other methods of metaphosphate generation, such as fragmentations of phosphoryl radicals, mixed phosphoric−carboxylic anhydrides or 2,4-bis(4-methoxyphenyl)-2,4-dithioxo-1,3,2,4-dithiadiphosphetane (Lawesson reagent), also have been developed; however, their applicability is limited to specific metaphosphate analogues.…”

A history of the Chemistry Department, University of Cape Town

“…Research flourished on several fronts during the existence of the Department of Organic Chemistry, the main areas being carbohydrate chemistry (Stephen, 1983(Stephen, , 1995(Stephen, , 2004Stephen et al, 1990); Cragg's steroid research and interest in borane chemistry (Cragg, 1975); Giles' synthetic group (Giles & Roos, 1976;Giles et al, 1979Giles et al, , 1984Giles et al, , 1994De Koning et al, 1991); Modro's active school of phosphorus chemistry (Modro, 1981;Hendrickse & Modro, 1984;Symes & Modro, 1986;Modro et al, 1987;Niven et al, 1988); Elsworth's work on the chemistry of marine organisms (Elsworth & Naude, 1986),and his participation in synthesis (Elsworth et al, 1988), and Campbell's burgeoning involvement in the chemistry and potential uses of fynbos constituents and medicinal plants (Campbell et al, 1980(Campbell et al, , 1986. The CSIR Fynbos Biome Research Unit was located on the top floor, otherwise occupied by the Department, and cooperation was maintained through its chemical director, a graduate of the Chemistry Department, Dr J.C. Patterson-Jones.…”

Phosphonic systems. Part 12. Fragmentation‐rearrangement of dialkyl 2‐acyloxyalkylphosphonates

“…The same two groups of researchers introduced an ingenious method of trapping the intermediate metaphosphate species via the phosphorylation of the surface OH groups in silica gel [S]. Our own work showed that metaphosphate esters, RO-P02, can be extruded under mild conditions from 2-arylethylphosphorochloridates [6] or mixed amidophosphoric-carboxylic anhydrides [7]. In all the examples listed, the molecule of a precursor can be considered as a system in which the metaphosphate X-PO2 has been "inserted" into a more complex molecular framework and can be "released" from that framework through the bond-breaking and bond-making fragmentation processes.…”