α-Chlorination and Carbonyl Olefination

Savignac, Philippe; Petrova, Jordanka; Dreux, M.; Coutrot, Philippe

doi:10.1055/s-1975-23839

Cited by 41 publications

(11 citation statements)

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“…We recently reported an efficient synthesis of diethyl dichloromethylphosphonate (1) 1 which is known as a useful precursor for the preparation of dichloroalkenes from carbonyl compounds on a large scale. [2][3][4][5] As a component of another project we required preparative access to symmetrical or unsymmetrical diarylalkynes for [4+2] cycloaddition reactions. There are several methods reported in the literature 6 for the synthesis of these types of alkynes and we will just mention the more relevant one.…”

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confidence: 99%

A Facile and High Yielding Synthesis of Symmetrical and Unsymmetrical Diarylalkynes Using Diethyl Dichloromethylphosphonate as Precursor

Mouriès¹,

Waschbüsch²,

Carran³

et al. 1998

Synthesis

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The reaction, under internal quench conditions, of diethyl dichloromethylphosphonate and symmetrical or unsymmetrical diaryl ketones in the presence of n-BuLi, leads to the corresponding symmetrical or unsymmetrical diarylalkynes via a Fritsch-Buttenberg-Wiechell rearrangement in a simple, high yielding, one-pot reaction.We recently reported an efficient synthesis of diethyl dichloromethylphosphonate (1) 1 which is known as a useful precursor for the preparation of dichloroalkenes from carbonyl compounds on a large scale. [2][3][4][5] As a component of another project we required preparative access to symmetrical or unsymmetrical diarylalkynes for [4+2] cycloaddition reactions. There are several methods reported in the literature 6 for the synthesis of these types of alkynes and we will just mention the more relevant one. Diarylalkynes are currently prepared via an oxidative coupling between aryl or substituted aryl halides and copper(I) acetylides in pyridine 7-9 or with terminal alkynes catalyzed by palladium at elevated temperatures. 10, 11 In the presence of copper(I) iodide, the palladium-catalysed reaction proceeds under mild conditions and gives the diarylalkynes in good yield. 12 This methodology has been widely used in the preparation of a variety of functionalised diarylalkynes. 11-16 Another approach uses the formation of diarylalkenes obtained by a Wittig-Horner reaction from arylmethylphosphonate esters and the corresponding aldehydes. After bromination of the alkenes and an elimination, effected with a base, the diarylalkynes are isolated. A recent preparation of dipyridylalkynes uses this process. 17 In the same way, [aryl(chloro)methyl]phosphonate has been introduced as an efficient reagent for the synthesis of phenylpyridylalkynes. 18,19 It is known that alkynes can equally be obtained through the Fritsch-Buttenberg-Wiechell rearrangement (1894) with 1,1-dibromoalkenes as starting materials. 20-22 Ihe reaction proceeds through the formation of an alkylidene carbene intermediate produced by an a-elimination of the 1,1-dibromoalkene (Scheme 1). However, as recently reported, the reaction is frequently non-specific, giving mixtures of compounds. [23][24][25] As previously described in our synthesis of chloroalkynes and terminal alkynes 1 we use internal quench conditions. Simultaneous addition of 1 and the prospective ketone 2 to LiHMDS in THF solution at low temperatures leads to a phosphorylated carbanion which is only present for a short period before it reacts with the ketone 2 to give the non-isolated gem-dichloroalkene 3. These conditions thus eliminate the possibility of decomposition of the phosphorylated carbanion to unwanted products. The reactions are easily monitored by 31 P NMR spectroscopy as on warming to room temperature the end of the first stage of the reaction is signalled by a single lithiophosphate peak [ 31 P NMR (THF): d = +0.4]. Next, the reaction medium is cooled to -60°C and two equivalents of n-BuLi are added followed by slow (40 min) warming to 0°C. This procedure gives ...

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confidence: 99%

A Facile and High Yielding Synthesis of Symmetrical and Unsymmetrical Diarylalkynes Using Diethyl Dichloromethylphosphonate as Precursor

Mouriès¹,

Waschbüsch²,

Carran³

et al. 1998

Synthesis

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“…16 The dibromomethylenecyclohexane 2 was obtained from 4-tert-butylcyclohexan-1-one via reaction with a mixture. 17 The cyclohexylidenethanol CBr 4 È(C 6 H 5 ) 3 P and -ethanoate derivatives 4 and 5 were obtained by WittigÈHorner reaction of the 4-tert-butylcyclohexan-1-one with triethyl phosphonoacetate, followed by reduction with lithium aluminium hydride.…”

Section: Methodsmentioning

confidence: 99%

Experimental Evidence for the Breakdown of the Karplus Relationship for3J(13C,1H) in1H—C—C=13C Systems

1997

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“…Thus as nucleophile 16 reacts at low temperature with alkyl iodides and activated alkyl bromide to give in high yields diethyl (1,1-dichloroalkyl)phosphonates (17), 51 it also reacts smoothly with aldehydes and ketones to give gem-dichloroolefins 18 through a Horner-Wadsworth-Emmons reaction (Scheme 13). 52 A large variety of carbonyl compounds can participate in the reaction, such as aliphatic and aromatic aldehydes, cyclic ketones, sterically hindered ketones, enolizable ketones, conjugated ketones, etc. Examples of this are shown in Table 2.…”

Section: A Reaction With Carbon Tetrachloridementioning

confidence: 99%

“…Thus as nucleophile 16 reacts at low temperature with alkyl iodides and activated alkyl bromide to give in high yields diethyl (1,1-dichloroalkyl)phosphonates ( 17 ), it also reacts smoothly with aldehydes and ketones to give gem- dichloroolefins 18 through a Horner−Wadsworth−Emmons reaction (Scheme ) …”

Section: Reaction With Carbon Tetrachloride/tetrabromide and Further ...mentioning

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Synthetic Applications of Dialkyl (Chloromethyl)phosphonates and N,N,N‘,N‘-Tetraalkyl(chloromethyl)phosphonic Diamides

et al. 1997

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α-Chlorination and Carbonyl Olefination

Cited by 41 publications

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A Facile and High Yielding Synthesis of Symmetrical and Unsymmetrical Diarylalkynes Using Diethyl Dichloromethylphosphonate as Precursor

A Facile and High Yielding Synthesis of Symmetrical and Unsymmetrical Diarylalkynes Using Diethyl Dichloromethylphosphonate as Precursor

Experimental Evidence for the Breakdown of the Karplus Relationship for3J(13C,1H) in1H—C—C=13C Systems

Synthetic Applications of Dialkyl (Chloromethyl)phosphonates and N,N,N‘,N‘-Tetraalkyl(chloromethyl)phosphonic Diamides

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