Philippe Savignac

Alkylidènediphosphonates et vinylphosphonates: une démarche synthétiques sélective par voie carbanionique

Abstract Phosphonoalkylation of acylchloro-phosphates or -phosphinates in the presence of excess lithium diisopropylamide leads to direct generation of lithiated methylene-diphosphonate anions. This stable type of anion can be either protonated in acidic medium to provide tetrasubstituted methylenediphosphonate or alkylatd. When aliphatic or aromatic aldehydes are added spontaneous formation of vinyl-phosphonates is observed. This process is a simple and convenient route to diphosphonic as well as to vinylphosphonic compounds.

Controlled monohalogenation of phosphonates: A new route to pure α-monohalogenated diethyl benzylphosphonates

Abstract Starting from diethyl benzylphosphonates, a wide variety of diethyl α-monofluoro, chloro, bromo and iodobenzylphosphonates have been obtained in pure form by a one-pot procedure. This high yielding method implies the intermediate protection of the benzyl anion with TMSCl followed by halogenation with an electrophilic halogenating reagent.

Synthese de phosphonates β-carbonyles: I. Par voie carbanionique

Abstract Condensation of a lithiated phosphonate carbanion not bearing a stabilizing group with a carbonyl precursor (amide or ester) gives an intermediate oxyanion which decomposes on hydrolysis to yield a β-carbonyl phosphonate. This type of reaction gives access to a large group of phosphonates: β-ketophosphonates, phosphonic aldehydes, phosphonopyruvates etc. The reaction conditions are discussed.

Dialkyl 1-Alkynylphosphonates: a Range of Promising Reagents

This review covers the preparations of 1-alkynylphosphonates by Michaelis–Arbuzov and Michaelis–Becker reactions, by nucleophilic substitutions at phosphorus (SNPV), and by elimination from 1-alkenylphosphonates. The reactivity and versatility of 1-alkynylphosphonates have made them valuable precursors for other phosphonates, and particularly for the synthesis of heterocycles by [2+2], [3+2], and [4+2] cycloaddition reactions.

Carbanions phosphonates α-lithiés: synthèse, basicité comparée et stabilité à l'autocondensation

Abstract Non stabilized α-lithio-α-substituted alkanephosphonates (RO)2P(O)CHR1Li (R1 = H, alkyl, C1) are commonly used as phosphonoalkylating agents. The strength of the conjugated acids (RO)2P(O)CH2R1 is estimated by concurrent metallation. The data checked range from phenylacetylene to toluene in relation with the inductive electronic effects of R and R1. Most of the α-phosphonyl carbanions give stable dimers via thermal self-condensation which is steric (R) and electronic (R1) effects dependent. In addition preparative conditions for some phosphonate precursors are reexamined.

Asymmetric hydrogenation of β-ketophosphonates and β-ketothiophosphonates with chiral ru (II) catalysts

Abstract Asymmetric hydrogenation of β-ketophosphonates and β-ketothiophosphonates is described. Enantiomeric excesses up to 99% were obtained.

A new route to α-fluorovinylphosphonates utilizing Peterson olefination methodology

Several α-fluorovinylphosphonates (6) have been synthesised from the Peterson olefination reaction applied to both aldehydes and ketones in conjunction with α-lithiated-α-fluoro-α-trimethylsilylmethylphosphonate (2). The reaction with aldehydes gives mainly the E-isomer whereas reaction with ketones gives mainly the Z-isomer. We propose a closed transition state to explain the results of our study.

A useful magnesium reagent for the preparation of 1,1-difluoro-2-hydroxyphosphonates from diethyl bromodifluoromethylphosphonate via a metal—halogen exchange reaction

Abstract When (EtO)2P(O)CF2Br (1) is treated with isopropylmagnesium chloride in THF at low temperature it gives a magnesium species (2) which undergoes reactions with strong electrophiles (HCl, TMSCl, halogens, aldehydes and ketones). The formation of products depends strongly on the reaction conditions. With 1.5 equivalents of 2 between −78 and 0°C, a conversion of more than 90% of aldehydes and ketones into 2-hydroxyphosphonates (7 and 8) can be achieved. These compounds (7 and 8) in the presence of base (NaH, LDA) are rearranged into 2,2-difluoroethylphosphates without concomitant formation of 1,1-difluoroolefines.

A new simple method for the synthesis of 1-alkynylphosphonates using (EtO)2P(O)CCl3 as precursor

Abstract 1-Alkynylphosphonates 4 were obtained from (EtO)2P(O)CCl3 1 and aldehydes in a one-pot procedure. It involves the formation of α-chlorovinyl phosphonate intermediates 3 by a Peterson olefination reaction followed by dehydrochlorination with LiHMDS.

Le O,O-diéthyltriméthylsilylchlorométhylphosphonate α-lithié (C2H5O)2P(O)C(Cl)Si(CH3)3Li: I. Préparations et propriétés

Abstract Silylation of either chloromethyl- or trichloromethylphosphonate in the presence of excess n-BuLi leads to the quantitative generation of lithiated trimethylsilyl-chloromethylphosphonates. This stable type of anion can be protonated, deuterated or alkylated. Compounds thus obtained can be desilylated in basic medium, or used for the preparation of α-bromo- and α-iodo-phosphonates after halogen-metal exchange. Condensation with aliphatic and aromatic aldehydes gives vinylphosphonates without stereochemical control.