Attack on Saturated Carbon

Arbuzov reactions of 4-acetoxyazetidin-2-one with phosphites or phosphonites gave the phosphonates (4) or phosphinates (5) which could be hydrolysed to the phospha-analogues (6) or (7) of aspartic acid.  

1 Attack on saturated carbon.- a-Hydroxyketones with diethyl-phosphorochloridite and ferric chloride gave 2-oxoalkylphospho-nates (1), probably via 2-oxoalkyl phosphites (2) which rearrange to (1) in the presence of the Lewis acid catalyst. No rearranged product was observed in the absence of the oxo group, and a-hydroxy esters gave the H-phosphonates (3). The 1,3,2-oxaza- 

Nucleophilic Reactions.—Attack on Saturated Carbon. Selected examples of the Arbusov reaction include phosphorylation of the chloroacetophenones (1) to give phosphonates, which cyclized to (2) in the presence of acid chlorides,1 formation of the azodiphosphonate (3) from 2,2 -dichloro-2,2 -azopropane,2 3 and the reaction of 2-chloro-3,4-dihydro-3-oxo-2//-l,4-benzothiazine (4) with triethyl phosphite to give the 2-phosphonate (5), which is used as an olefin synthon.8 Bis(trimethylsilyl) trimethylsiloxymethylphosphonite (6) has been synthesized by silylation of hydroxy-methylphosphonous acid, and, as expected, undergoes a normal Arbusov reaction with alkyl halides to give the phosphonates (7).4 This series of reactions, followed by 

Silylated iminophosphines (15) react with alkyl halides to give the iminophos-phoranes (16).8 Similar reactions with Main-group IV and VII halides give the heterocycles (17) via the intermediate 1,2-addition products (18), which can be isolated in the case of germanium. 

Nucleophilic Reactions.—Attack on Saturated Carbon. Numerous undistinguished examples of the Arbusov reaction have appeared, mostly in the Russian literature. The reaction has been used to prepare the phosphonate analogue (1) of the initial 

Aminomethanebisphosphonic acid derivatives (11) have been prepared by a number of methods, including the reaction of diethyl phosphite with amino-acetals and the reaction of triethyl phosphite with the halogenoiminium salts (12). 

Nucleophilic Reactions.—Attack on Saturated Carbon. The Arbusov reaction has been widely used in phosphonate synthesis. This has been extended to the preparation of the unsymmetrical diphosphine ligand (2) through reaction of 

2-Chloromethyloxazine (3) reacts with phosphines and phosphites to give 

A variety of Arbusov intermediates have been prepared from phosphites and alkyl halides and studied by n.m.r. spectroscopy. In cases with simple alkyl substituents the intermediates (7) could not be detected however, (8) 

A new synthesis of a)S-unsaturated acids has been developed through alkylation of dibenzyl phosphite anion followed by carboxylation to give the phosphonate (11), which gives the olefin on reaction with aldehydes and two 

Under more forcing conditions, sulphur analogues [e.g. EtSPEt2] of tervalent phosphorus acids also undergo the Arbusov reaction with alkyl halides.  

The low reactivity of aromatic halides in the Arbusov reaction has been partially overcome through the use of palladium catalysts. The reaction of phosphites with diphenyliodonium iodide in the presence of copper salts gives arylphosphonates (1), presumably by initial nucleophilic substitution and an Arbusov reaction. Anionic resins also appear to catalyse the 

Arbusov reaction, causing rearrangement of the cyclic phosphite (2) to the phosphonate (3) even at — 5 °C. 

A mixture of acetylenic (4) and allenic (5) products has been obtained from the reaction of propargyl bromide with triethyl phosphite.  

Nucleophilic Reactions.—(/) Attack on Saturated Carbon. The Arbusov reaction has been used to prepare organosilicon-substituted phosphonates (1) and phosphorylated ethers (2a) and sulphides (2b). Bromo- and chloro-derivatives of the cyclic phosphite (3) do not react with ethyl halides 

The mechanism of the Arbusov reaction has been the subject of some study. Intermediates (4), isolated at low temperatures from the reaction of phosphonites with alkyl halides, show n.m.r. chemical shifts in the region of — 95 p.p.m. in a wide variety of solvents.  

In view of these results a new mechanism is suggested with initial reversible formation of a quinquecovalent intermediate (9), followed by 

An earlier report that diethyl t-butylphosphonite (10) did not undergo an Arbusov reaction, presumably for steric reasons, has been withdrawn since the presumed phosphonite is now shown to be the phosphonate. 

Trippett and Stewart have shown that the phosphonium salts (11) derived from the reaction of phenyl di-t-butylphosphinite (12) with alkyl halides are highly resistant to hydrolysis and they suggest that this is due to the reluctance of phosphorus to accommodate two t-butyl groups in a trigonal-bipyramidal intermediate. 

The chiral acetals (10) are attacked by triethyl phosphite at low temperatures in the presence of titanium(IY) chloride to give 1-alkoxyphosphonates (1 la,b) with a high degree of diastereoselecti-vity the main diastereomers (11a) were purified and used to prepare pure (S)-enantiomers of a-aminophosphonic acids. Phosphono-, phenylphosphinico-, and diphenylphosphinoyl-sarcosine (12) have been prepared in improved yields by Arbuzov reactions on the protected sarcosine derivative (13).7 

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Nucleophilic attack on saturated carbon atom (feading to substitution... 

Nucleophilic attack on saturated carbon atoms, leading to substitution reactions... 

Attack on Saturated Carbon.—The kinetics and mechanism of Arbuzov reactions of several phosphonous and phosphinous acid esters have been studied with the use of and n.m.r. The nucleophile of the dealkylation step is either X" or (1), depending on X (Scheme 1). Tetraphenyl methylenebis(phosphonate)... 

Attack on Saturated Carbon. - Ethylene dicarboxylic diphosphonic acid (EDCP, 2) has been prepared in 70% yield from 2,3-dichlorosuccinic anhydride (3) and trimethyl phosphite, followed by hydrolysis of the Arbuzov product. Tris(trimethylsilyl) phosphite, in contrast to trialkyl phosphites, attacks an oxirane carbon of epibalohydrins (4) to give the phosphonates (5). Bis(trimethylsilyl) phosphonite (6) has previously been prepared in situ and used to obtain y-ketophosphinic acids similar reactions with simple alkyl halides to give alkylphosphinic and dialkylphosphinic acids acids in high yields have now been described. ... 

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