Attack on Unsaturated Carbon

Attack on Unsaturated Carbon. The annual addition of phosphites to every variety of activated double bond continues. These include nitro-alkenes,9 a/S-unsaturated carboxylic acid derivatives,10 maleimides,11 fulvenes,12 and pyridinium salts.13 The reaction of diethyl phosphite with keten 0,N-, S,N, and Al,AT-acetals has been used to prepare the enamine phosphonates (19).14 

The a/ -unsaturated thioketone (20) undergoes Michael addition of trimethyl phosphite to give (21), which cyclizes to (22).15 A similar addition of benzylalkyl (or 

Further studies of the reactions of secondary and tertiary phosphites with cyclo-pentadienones have included the keto-cyclone (26), which gives the phosphonates (27) and (28), respectively.18 Ketenphosphoranes (29) have been prepared by the reaction of diphenylcyclopropenone with a variety of tervalent phosphorus compounds.19 

Recently reported additions of dibutyl phosphinite20 and tetra-alkoxydiphos-phines21 to alkenes are probably of free-radical nature, although the reactions only take place with alkenes possessing electron-withdrawing groups. 

The usual flood of reports concerning the addition of phosphites to imines has appeared. These include the reaction of hypophosphites to give a-aminoalkyl-phosphinic acid salts possessing antibacterial activity22 and the synthesis of AM, 4,2-A5-oxazaphospholines (30) from phosphites and carboxamides.23 The addition of 

Attack on Unsaturated Carbon. The Russian literature contains the usual examples of the addition of tervalent phosphorus to activated double bonds. The reaction of tri-ethyl phosphite with 1,2-dichIorovinyl ethers to give the phosphonate (13) is in 

Di-isopropyl pyridyl-4-phosphonates (18) are the exclusive products of the reaction of sodio di-isopropyl phosphonate with 1-triphenylmethylpyridinium salts, even in the cases of salts with no a-substituents. Surprisingly, the vinylphosphonate 

As might be expected, keto-sugar acetates undergo the Perkow reaction with trimethyl phosphite to give a mixture of enol phosphates (27) and (28). In other cases the products appear to be dependent on the leaving group, and the Perkow products 

Examples of the reaction of tervalent phosphorus with isocyanates and their analogues include the addition of phosphites to carbonyl isothio- and isoseleno-cyanates to give the phosphonates (32) and the reaction of dialkyl phosphoramidites with trichloroacetyl isocyanate to give the rearranged product (33). Predictably, the betaine (34) is obtained from the reaction of TDAP with fluorosulphonyl isocyanate more surprising is the relative stability of (34) to hydrolysis.  

Acetonitrile undergoes aeid-catalysed addition of two moles of diethyl phosphite to give 1-aminoethyldiphosphonic acid derivatives (35).  

Attack on Unsaturated Carbon. Numerous reports of addition of tertiary phosphites, secondary phosphites, and silyl phosphites to activated olefins have appeared. The addition of secondary phosphites to acryloyl chloride in the presence of trimethylsilyl azide provides a route to 2-isocyanato-ethylphosphonates (13).  

Cycloalkenyldiphosphonates (14) ha been prepared from the corresponding dichloride by reaction with tertiary phosphites. A similar 

Paulsen has continued his investigation of the addition of secondary phospliites to unsaturated carbohydrates. The same mixture of a- and P-phosphonates is obtained from the reaction of either triacetate (17) or (18) 

The reaction of tervalent phosphorus amides containing a NH with activated olefins predictably gives phosphine imines, e.g. (24), through addition and proton transfer. 

The phosphonate (25) has been obtained in moderate yield from the reaction 

Attack on Unsaturated Carbon. The addition of tervalent phosphorus nucleophiles to a wide range of activated olefins, including barbituric 

Dibutyl acetyl phosphite and acrolein react to give the phosphonate (16) in low yield. A cyclic mechanism is suggested, but an intermolecular reaction would seem equally possible. The analogous product (17) is obtained from a similar reaction of the germyl phosphite (18). 

The reaction of phosphites with trifluoromethyl-substituted 2-aza-l,3-butadienes (19) gives the adducts (21), the structure and stereochemistry 

Schmidpeter has reported a novel 1,3-cycloaddition reaction of methyleneaminophosphines to activated double and triple bonds. Acrylic acid derivatives give the azaphospholens (23), while acetylenes give azaphospholes (24). 

Burger, J. Fehn, J. Albanbauer, and J. Friedl, Angew. Chem. Intermit. Edn., 1972, 

Attack on Unsaturated Carbon.—A new route to arenephosphonates (10) via Cul-promoted Michaelis-Becker reactions has been reported. The method is particularly useful for hindered aryl halides in the presence of certain functional groups (NHa, OMe). The details of further studies of the use of Cu complexes of trialkyl phosphites to prepare vinylphosphonates have been published.  

The reaction of triethyl phosphite with maleic anhydride has been re-investi-gated. The product is not the dimeric phosphorane (11), but the ylid (12). Reactions of alkyl or aryl diphenylphosphinites with 1-nitro-l-alkenes have been studied in detail. Radical ion-pairs are involved as shown by e.s.r. and P CIDNP experiments. Allene may be hydrophosphorylated in a radical-initiated process to give allyl- and isopropenyl-phosphonates. A phosphorane (14) has been observed during the reaction of ethyl diethylthiophosphinite (13) with methacrylic acid.  

A series of N-propargylaminophosphines (15)—(19) has been prepared in order to study their propensity to rearrange (15)—(17) were thermally stable, but (18) and (19) rearranged spontaneously to the A-methyl-3-phosphinopro-penal imines (20) and (21), respectively. This contrasts with the behaviour of the analogous propargyloxy compounds (22) which give allenic phosphine oxides.  

Trippett, in Organophosphorus Chemistry , ed. D. W. Hutchinson and S. Trippett (Specialist Periodical Reports), The Royal Society of Chemistry, London, 1979, Vol. 10, p. 49. 

2 Attack on Unsaturated Carbon.- A versatile route to phosphinic acids (15) is the 1,4-addition of bis(trimethylsilyl) phosphonite (16) to a,p-unsaturated esters.The pyrophoric (16) was prepared in s/fu from triethylammonium phosphinate silylation and 1,4-addition can be repeated to give (17), or performed in one step if symmetrical phosphinic acids (17) are wanted. Tervalent phosphorus acid esters (18) react with dialkyl acetylenedicarboxylates in the presence of carbon dioxide to give 1,2-oxa-phospholenes (19) these reacted further with an excess of the phosphorus reagent to give different ylids, (20) or (21), dependant on the number of methoxy groups in (18). 

Dialkyl 1-alkynylphosphonates (22) were formed in good to high yields by treatment of 1-alkynyliodonium tosylates (23) with trialkyl phosphites the reaction is exothermic with trimethyl phosphite but requires heating with triethyl or triisopropyl phosphite. The addition of trimethyl or triethyl phosphite to 3-alkylene-2-oxindoles (24) has led to new product types for a, -unsaturated carbonyl compounds, i.e. a stable tri-alkoxyphosphonium zwitterion (25), and a C-alkylated phosphonate (26).  

The thiophosphite (27) with acetyl chloride gave mainly the Arbuzov product (28) in methylene chloride, but the substitution product (29) was the main product in hexane or without solvent, probably because the intermediate is a phosphorane in the latter case. 2-Acetylphenyl alkylphosphonamidites, phosphorodiamidites, or phos-phoramidites (30) upon heating gave different cyclisation products (31)-(33) dependant on the substituents on phosphorus, and on the amount of amine hydrochlorides present in (30).  

2 Attack on Unsaturated Carbon.- Ethyl trimethylsilyl (di-ethoxymethyl)phosphonite (11) has been used to prepare a series of 0-, p-, and 7-aminoalkylphosphonous acids, e.g. (12) and 

Diethyl formylphosphonate (24) can be prepared from triethyl phosphite and acetic formic anhydride, but is thermally unstable. It eliminates carbon monoxide at -10 °C giving the phosphate (25) 

Symmetrical monothio- and monoselenopyrophosphate esters (36) have been prepared in high yields from dialkyl trimethyl-silyl phosphites and the sulphenyl or selenenyl chlorides (37) 

A review on the reaction of tervalent phosphorus acid derivatives with halogens has appeared. Alkylbis(diisopropyl-amino) phosphines (41) react with carbon tetrachloride or bromotrichloromethane to give the P-halogeno ylides (42) below 0 The ylides rearrange to the substituted phosphines (43) 

2 Attack on Unsaturated Carbon. - A new method to obtain a-amino phosphonic acids (7) in high enantiomeric excess involves the selective addition of trimethyl phosphite to chiral oxazolidines (8). The reaction probably occurs by 

A full paper has appeared on the preparation of P-chiral fullerenephosphinites reported last year. A series of functionalised alkylphenylphosphinic acids has been synthesised by addition of in situ prepared bis(trimethylsilyl) phenylphos-phonite (12) to a range of electrophiles, e.g. (IS). Stereoselective syntheses of the four diastereomers of phosphothreonine have been described which are based on the stereoselective addition of diethyl trimethylsilyl phosphite (14) to protected lactaldehyde (15) or its imine. A similar procedure gave access to phosphomycin 

Some 1,2-dihydroisoquinoline-l-ylphosphonates, e.g. (18), have been prepared from trialkyl phosphites, isoquinoline, and a sulfonyl chloride. Quinoline gave similarly the corresponding l,2-dihydroquinoline-2-ylphosphonates. The superbase (19) has been shown to be a very effective catalyst for the acylation of hindered and/or acid-sensitive alcohols with benzoic anhydride a P-acylated intermediate (20) was inferred from NMR data. 

2 Attack on Unsaturated Carbon.- Bis(trimethylsilyl)phosphonite (14), prepared from ammonium phosphinate and hexamethyldisilazane, adds to o,p-unsaturated ketones (IS) to give high yields of mono- or disubstituted phosphinic acids. Low yields were obtained for enolisable ketones if (14) was prepared in situ from trimethylsilylchloride and triethylamine instead. Diethyl trimethyl-silyl phosphite (16) reacts readily with a,p-unsaturated imines to give solely 1,2-addition products (17), even in the presence of bulky Y-substituents, provided R Ws an aryl group.  

Formaldehyde dimethylhydrazone and phosphorus tribromide gave the unstable phosphonous dibromide (18) which could be converted to a distillable phosphonous diamide (19). Phosphorus tribromide reacts with 2-methylfuran in a 1 1 molar ratio to give 5-methyl-2-furanylphosphonous dibromide (20) a 1 2 molar ratio gave the pure bis(furanyl)phosphinous bromide. Unsubstituted 

PBrg + CH2=N-NM02 Br2P-CH=N-NMe2 — (Me2N)2P-CH=N-NMe2 

Some dicarbonyl(ri5-cyclopentadienyl)iron substituted alkylphosphonates (23), containing one or two nucleosidyl groups, have been prepared from the iron-ethylene complex (24) and trialkyl phosphites.  

A -Acyl salts of nitrogen heterocycles phosphorylate in the hetero-ring, rather than at the carbonyl group, to give, for example, (25). The addition of dialkyl phosphites to ynamines has been reported. The products 

A number of additions of secondary phosphites to Schiff bases have 

A kinetic study of the previously reported substitution of aromatic nitro groups by tervalent phosphorus has established an aromatic 5n2 mechanism. Similarities in values of activation energies, and in relative reactivities of phosphite and phosphonite esters, between this displacement and the Arbusov reaction suggest a related mechanism (31), while the lack of reactivity of p-dinitrobenzene is attributed to the need for intramolecular solvation (32). The exclusive formation of ethyl nitrite, rather than other isomers, is confirmed from the decomposition of triethoxy-(ethyl)phosphonium fluoroborate (33) in the presence of silver nitrite. A mechanism involving quinquevalent phosphorus (34) still seems applicable, particularly in view of the recent mechanistic work on the Arbusov reaction.  

The reaction of tetraphenylcyclopentadienone (tetracyclone) with dialkyl phosphites has invoked further interest. Miller has shown that reactions at 20 °C in the presence of sodium bicarbonate lead to products (35) and (36), with phosphorus substituted at carbon rather than oxygen. Quite different products (37) and (38) are obtained at 160 °C, although whether (38) is obtained from initial attack at oxygen or carbon is still unresolved. 

Organophosphorus Chemistry, Volume 29 The Royal Society of Chemistry, 1999 

An efficient route to enantiopure piperidin-2-ylphosphonic acid (10) has been published. It involves a tin tetrachloride catalysed addition of trimethyl phosphite to the oxazolopiperidine II to give 12, which could be separated in pure diastereomers. 

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Attack on Unsaturated Carbon.- Several bis(trimethylsilyl) aryl-... 

Attack on Unsaturated Carbon.- Tervalent phosphorus compounds are effective catalysts for the polymerization of acrylic acid derivatives, and the monomeric adducts which initiate the polymerization usually cannot be isolated. However, by addition of ethyl 2-cyanoacrylate to strongly nucleophilic tervalent phosphorus compounds it was possible to isolate monomeric adducts,... 

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