Trialkyl phosphonoacetates

In principle, reaction 22 may be extended to the preparation of the products 394 with n having any value >1, and conventional reactions have thus been carried out with 3-halo-propanoic " 4-halobutanoic, 5-chloropentanoic and 6-bromohexanoic acid derivatives. Triethyl 3-pho honopropanoate has also been obtained from triethyl phosphite and j5-propiolactone although a normal Michaelis-Arbuzov reaction occurs between trialkyl phosphites and a-bromobutyrolactones (3-bromotetrahydrofuran-2-ones) from which the anhydrides 396 (R = H or Me) have been obtained Difficulties may be encountered should the carbon chain of the acid derivative be branched for example, whereas Michaelis-Arbuzov reactions proceed satisfactorily with primary alkyl halides, and generally also with secondary alkyl halides , the use of tertiary alkyl halides is rarely, if ever, satisfactory. Compounds branched on the a-carbon atom may also be prepared, in principle, by the alkylation of trialkyl phosphonoacetates. 

Condensation of 2-nitrosodiphenylamines with a variety of highly stabilized carbanions of dialkyl malonates, alkyl phenylacetates, and trialkyl phosphonoacetates is an efficient way for the synthesis of a great deal of substituted iV-arylquinoxalin-2 (l//)-ones (Scheme 101) [235, 236]. Double additions of anions of 2-cyanoalkyl carboxylates to 2-nitroso-4-alkylaminodiphenylamines result in the formation of pyrroloquinoxaUnones [236]. 

A DFT study of the origins of stereoselectivity in the aldol reaction of bicyclic amino ketones (20) with aromatic aldehydes has been reported (Scheme 18). ° Base-catalysed direct aldolization of a-alkyl-a-hydroxy trialkyl phosphonoacetates with aldehydes proceeds via a fully substituted glycolate enolate intermediate formed by a [l,2]-phosphonate-phosphate rearrangement. High enantioselectivity can be achieved by the application of chiral iminophosphorane catalysts. 

The protected methyl glycoside 3 is converted to the corresponding aldehyde by Swern oxidation using oxalyl chloride activated DMSO. Further reaction with triethyl phosphonoacetate and sodium hydride -known as the Horner-Wadsworth-Emmons reaction - provides selectively the trans et /Tun saturated ester 4 in 72 % yield. This valuable alternative to the Wittig olefination protocol uses phosphonate esters as substrates which are readily available from alkyl halides and trialkyl phosphites via the Arbuzov rearrangement.9 co2Et Reaction of the phosphonate with a suitable base gives the... 

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