Reactions of acyl phosphonates with organoaluminum reagents: a new method for the synthesis of secondary and tertiary α-hydroxy phosphonates

The reactions of organoaluminum reagents (trimethylaluminum, triethylaluminum, etc.) with aryl and alkyl acyl phosphonates, which lead to the formation of α-hydroxy phosphonates in moderate to good yields, are reported. This method provides easy access to secondary and tertiary α-hydroxy phosphonates depending on the reaction conditions. The reactions of triethylaluminum with a series of acyl phosphonates at 0 °C gave the secondary α-hydroxy phosphonates, while at −100 °C they afford the tertiary α-hydroxy phosphonates.     

Cyanide ion promoted addition of acyl phosphonates to ethyl cyanoformate: synthesis of tertiary carbinols via tandem carbon-carbon bond formations

New cyanation/phosphonate-phosphate rearrangement/C-acylation reactions of cyanophosphate anion with cyanoformate esters are described. Phase-transfer cocatalysts facilitate cyanide-catalyzed reactions between acyl phosphonates and cyanoformates to afford protected tertiary carbinol products in good to excellent yields (74-95%). Ethyl cyanoformate is used as a cyanide source and electrophile. The scope of the reaction was investigated by using a number of benzoyl and acyl phosphonates along with ethyl cyanoformate. Representative chemoselective reduction of the product 5a afforded ethyl 3-amino-2-hydroxy-2-phenylpropanoate (13) in good yield.     

Addition of trifluoromethyltrimethylsilane to acyl phosphonates: synthesis of TMS-protected 1-alkyl-1-trifluoromethyl-1-hydroxyphosphonates and 1-aryldifluoroethenyl phosphates

Addition reactions of nucleophilic CF3TMS to acyl phosphonates were investigated. Various acyl phosphonates reacted readily with CF3TMS in the presence of K2CO3 in DMF at rt to give 1-alkyl-2,2,2-trifluoro-1-trimethylsilyloxyethylphosphonate in 70-90% yields. When benzoyl phosphonates were used as starting material, after addition of CF3, the formed alcoholate undergoes phosphonate-phosphate rearrangement to form the acyl anion, followed by elimination of F- to give 1-aryldifluoroethenyl phosphates in 87-97% yields. As a representative example, vinylphosphate 6a was converted into 2,2-difluoro-1-phenylethanone 7 with 6 N HCl/EtOH/reflux or CAN/NaOH/MeOH/0 degrees C in 82-90% yields.     

Reactions of dialkyl phosphonates and phosphonates with bis(benzylideneimino)toluene

Dialkyl phosphonates bind to the C=N bond of bis(benzylideneimino)toluene, with formation of dialkyl (benzylideneimino)benzylaminobenzyl phosphonates. The complicated character of IR spectra of these compounds is connected with the possibility of formation of dimeric cyclic associates and intramolecular hydrogen bonding. Phosphinic acid reacts with bis(benzylidenimino)toluene in a 2: 1 ratio to affordN,N-benzylidenebis(-amino-benzytphosphonic) acid.Translated fromIzvestiya Akademii Nouk. Seriya Khimicheskaya, No. 5, pp. 1303–1305, May, 1996.     

The efficient synthesis of 2-arylpyrimidine acyclic nucleoside phosphonates using Liebeskind-Srogl cross-coupling reaction

A series of novel acyclic nucleoside phosphonates with various aryls attached to the C-2 position of the pyrimidine moiety has been prepared using the Liebeskind-Srogl cross-coupling protocol. The reactions of highly functionalised 2-(methylsulfanyl)pyrimidines with various arylboronic acids were studied and optimised.     

First general approach to cyclohex-3-ene-1,1-bis(phosphonates) by Diels-Alder cycloaddition of tetraethyl vinylidenebis(phosphonate) to 1,3-dienes

Tetraethyl vinylidenebis(phosphonate) (VBP) reacts smoothly with substituted 1,3-dienes at 90-110 degrees C without solvent to give the corresponding cyclohex-3-ene-1,1-bis(phosphonates) in good yields (60-85%). With nonsymmetrically substituted dienes, mixtures of regioisomers are obtained, the regioisomeric ratio being exclusively controlled by electronic effects. Danishefsky's diene allows tetraethyl 4-oxocyclohex-2-ene-1,1-bis(phosphonate) to be obtained in an 81% overall yield after the acid-catalyzed hydrolysis of the Diels-Alder cycloadduct. With 2,3-dimethoxy-1,3-butadiene, a mixture of regioisomeric dimethoxycyclohexene-1,1-bis(phosphonates) is formed by the VBP-catalyzed isomerization of the normal Diels-Alder cycloadduct. The mixture converges into tetraethyl 3,4-dimethoxycyclohex-2-ene-1,1-bis(phosphonate) at prolonged reaction times.     

Interactions of carborane-containing electrophiles with triethyl phosphite. Synthesis of new carborane-containing phosphonates

The reactions ofo-carboran-l-ylethyl mesylates with triethyl phosphite and sodium diethyl phosphite were studied. Carborane-containing phosphonates were synthesized. The reaction ofo-carboranylacetyl chloride with triethyl phosphite affordedO,O-diethyl (E)-2-(o-carboran-l-yl)-1-(o-carboran-1-ylacetoxy) vinylphosphonate rather than oxo phosphonate. Dedicated to the memory of Academician M. I. Kabachnik on his 90th birthday. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2041–2044, October, 1998.     

二硝基苯乙基氟代膦酸二乙酯的制备

在室温下,二氟溴甲基膦酸二乙酯与锌粉反应生成锌试剂;2,4-二硝基氯化苄与合成的锌试剂在溴化亚铜催化作用下即可反应生成二硝基苯乙基(氟代)磷酸二乙酯化合物。两步反应都可在室温下进行,操作简单易行。     

Convenient synthesis of α,β-unsaturated phosphonates via a Mizoroki-Heck reaction of arylboronic acids with diethyl vinylphosphonate

Palladium acetate catalyzed Mizoroki-Heck reactions of arylboronic acids with diethyl vinylphosphonates afford α,β-unsaturated phosphonates in good yields.     

Synthesis of nonracemic allylic hydroxy phosphonates via alkene cross metathesis

Allylic hydroxy phosphonates and their derivatives can be interconverted by using cross metathesis with second generation Grubbs catalyst. The absolute stereochemistry of the starting phosphonate is conserved in the product. Cross metathesis reaction of the acrolein-derived phosphonate 2a yields a series of functionalized allylic hydroxy phosphonates. However, the cross metathesis reaction is often accompanied by competing dimerization and alkene migration reactions leading to a reduction in yield. The cinnamaldehyde- and crotonaldehyde-derived phosphonates 2b and 2c were also examined. In general, the metathesis reactions of phosphonates 2b and 2c are considerably slower than those for phosphonate 2a leading to mixtures. Several hydroxyl-protected derivatives of the phosphonate 2a (methyl carbonate 3a, acetate 4a, N-tosyl carbamate 5a, TBDMS 6a, and acetoacetate 7a) undergo metathesis without competing side reactions to give substituted allylic phosphonates in good to excellent yield.     

Modified horner–emmons reaction of polymeric phosphonates: Versatile synthesis of pendant stilbene-containing polymers

Poly[styrene-co-(diethyl vinylbenzylphosphonate)] and poly[methylmethacrylate-co-(diethyl vinylbenzylphosphonate)] were prepared and used in modified Horner-Emmons reactions to synthesize polymers with covalently attached stilbene groups. This versatile new method allowed for the preparation of polymers with either electron-donor (OCH₃, CH₃) or electron acceptor (Br, NO₂) substituents on the stilbene aromatic ring. The resulting polymers were characterized by ¹H NMR, FT-IR, UV-visible, DSC, and size exclusion chromatography. Efficient transformation of polymeric phosphonates to the polymeric stilbene derivatives was realized. Size exclusion chromatographic analyses demonstrated that the reaction conditions have no deleterious effect on the molecular weight distribution of the various polymers that were prepared. Photochromic behavior was demonstrated for one of the derivatives. © 1995 John Wiley & Sons, Inc.     

Highly enantioselective synthesis of 2,6-disubstituted and 2,2,6-trisubstituted dihydropyrones: a one-step synthesis of (R)-(+)-hepialone and its analogues

An efficient enantioselective approach to chiral dihydropyrones has been developed by the hetero-Diels-Alder (HDA) reactions of (E)-4-methoxy-2-trimethylsiloxy-penta-1,3-diene (diene 1) with aldehydes and pyruvates. It has been found that the readily accessible (R)-BINOL-Ti(OiPr)(4) (1.1:1) complex was a very effective catalyst for this reaction. Aromatic, heteroaromatic, conjugated, and aliphatic aldehydes afforded the corresponding products in moderate to high isolated yields (up to 99%) with excellent enantioselectivities (up to 99% ee). The first example of highly enantioselective synthesis of 2,2,6-trisubstituted dihydropyrones by the catalytic reaction of diene 1 with pyruvates was reported. The isolated intermediates indicated that this asymmetric HDA reaction proceeded in a Mukaiyama aldol pathway. On the basis of the absolute configurations of the products, a possible mechanism was proposed. Moreover, the catalytic system could be used to synthesize a series of enantioenriched beta-hydroxyketones 4. Finally, this methodology was successfully applied for the one-step synthesis of the important natural product (R)-(+)-Hepialone with 88% isolated yield and 94% enantioselectivity.     

Synthesis of N-(alkoxycarbonyl or alkoxycarbonyl-methyl-alkoxyphosphonyl)-α-amino-O, O-diphenyl phosphonates and their bioactivities

With phosphonoformic acid (PFA) and its analog, phosphonoacetic acid (PAA), as the lead compounds, α-amino phosphonates were introduced into PFA and PAA. The derivatives of N-(alkoxycarbonyl-alkoxyphosphonyl)-α-amino phosphonates (I) and N-(alkoxycarbonyl-methyl-alkoxyphosphonyl)-α-amino phosphonates (II) with the N-terminal of amino phosphonates bonding to phosphorus atom of PFA andPAA were synthesized via the reaction of the corresponding phosphonyl chloride with α-amino phosphonates in the presence of a base. The³¹P NMR spectra of I and II were determined. It is found that the coupling constants³ J _pp with R³ being alkyl group were lower than those with R³ being (substituted) phenyl, and this result was discussed. The preliminary bioassay showed that some of the compounds I and II have better activities against tobacco mosaic virus (TMV). The inhibitory was higher than that of DHT (2, 4-dioxyhexahydro-1, 3, 5-triazine). In addition, some of the compounds showed the activity against cancer cells. Project supported by the National Natural Science Foundation of China.     

The development for the synthesis of chiral acyclic nucleosides and their phosphonates

Acyclic nucleosides and their phosphonates possess significantly antiviral and cytostatic activities. For acyclic nucleosides and their phosphonates, the introduction of a chiral group to their side chain or the absolute configuration of the chiral atom could affect their biological activities obviously. Thus, the asymmetric synthesis of chiral acyclic nucleosides and their phosphonates has received continuous attention. The previous reports mainly focus on employing the chiral pool and chiral auxiliary methods for the synthesis of chiral acyclic nucleosides and their phosphonates. In contrast, the asymmetric catalysis methods for the synthesis of acyclic nucleosides and their phosphonates are still in the beginning. This digest paper will serve to highlight the significant progress that has been made in these areas.     

New mixed phosphonate esters by transesterification of pinacol phosphonates and their use in aldehyde and ketone coupling reactions with nonstabilized phosphonates

Alkylpinacol phosphonates were prepared by rhodium-catalyzed olefin hydrophosphorylation, and attempted alpha-deprotonation of the pinacol derived alkyl phosphonates resulted in ring cleavage. The propensity of the alkylpinacol phosphonates to undergo ring opening was exploited to prepare phosphonic acid monomethyl esters in high yield by transesterification in acidulated methanol. Esterification and alkylation with aldehydes or ketones gave beta-hydroxy mixed phosphonate esters. tert-Butyl and benzylic phosphonate ester protective groups were introduced to improve the efficiency and functional group compatibility of beta-hydroxy phosphonate saponification. The beta-hydroxy phosphonic acid monomethyl esters were dehydrated with diisopropylcarbodiimide, which gave oxaphosphetane intermediates that collapse to an olefin. The overall reaction sequence complements the arsenal of Horner-Wadsworth-Emmons-type coupling reactions.     

Rhodium-catalyzed enantioselective hydrogenation of unsaturated phosphonates by ClickFerrophos ligands

Newly developed ClickFerrophos II ligands were applied in the hydrogenation of α,β-unsaturated phosphonates. The use of a rhodium/ClickFerrophos II catalyst was examined in the hydrogenation of functionalized α,β-unsaturated phosphonates and was revealed to be effective for β-alkyl-β-aryl or β-dialkyl phosphonates, (Z)-β-enolester phosphonates, and α-phenylethenyl phosphonates, producing the corresponding chiral phosphonates in good yields with high enantioselectivities (up to 96% ee).     

Enantiopurity analysis of new types of acyclic nucleoside phosphonates by capillary electrophoresis with cyclodextrins as chiral selectors

CE methods have been developed for the chiral analysis of new types of six acyclic nucleoside phosphonates, nucleotide analogs bearing [(3‐hydroxypropan‐2‐yl)‐1H‐1,2,3‐triazol‐4‐yl]phosphonic acid, 2‐[(diisopropoxyphosphonyl)methoxy]propanoic acid, or 2?(phosphonomethoxy)propanoic acid moieties attached to adenine, guanine, 2,6‐diaminopurine, uracil, and 5‐bromouracil nucleobases, using neutral and cationic cyclodextrins as chiral selectors. With the exception of the 5‐bromouracil‐derived acyclic nucleoside phosphonate with a 2‐(phosphonomethoxy)propanoic acid side chain, the R and S enantiomers of the other five acyclic nucleoside phosphonates were successfully separated with sufficient resolutions, 1.51–2.94, within a reasonable time, 13–28 min, by CE in alkaline BGEs (50 mM sodium tetraborate adjusted with NaOH to pH 9.60, 9.85, and 10.30, respectively) containing 20 mg/mL β‐cyclodextrin as the chiral selector. A baseline separation of the R and S enantiomers of the 5‐bromouracil‐derived acyclic nucleoside phosphonate with 2‐(phosphonomethoxy)propanoic acid side chain was achieved within a short time of 7 min by CE in an acidic BGE (20:40 mM Tris/phosphate, pH 2.20) using 60 mg/mL quaternary ammonium β‐cyclodextrin chiral selector. The developed methods were applied for the assessment of the enantiomeric purity of the above acyclic nucleoside phosphonates. The preparations of all these compounds were found to be synthesized in pure enantiomeric forms. Using UV absorption detection at 206 nm, their concentration detection limits were in the low micromolar range.     

An efficient and recyclable silica‐supported carbene–Cu(II) catalyst for the oxidative coupling reaction of terminal alkynes with H‐phosphonates under base‐free reaction conditions

The oxidative coupling reactions of terminal alkynes with H‐phosphonates were explored using SiO₂−NHC−Cu(II) (5.0 mol%) as catalyst at room temperature under base‐free reaction conditions. The reactions of a variety of terminal alkynes with H‐phosphonates generated the corresponding alkynylphosphonate products in good to excellent yields. In addition, SiO₂−NHC−Cu(II) could be recovered and recycled for six consecutive trials without significant loss of its reactivity. Copyright © 2011 John Wiley & Sons, Ltd.     

Allylic hydroxy phosphonates: versatile chiral building blocks

Allylic hydroxy phosphonates are converted into β and γ substituted amino phosphonates using a series of palladium-catalyzed reactions. The judicious selection of nitrogen nucleophile and palladium catalyst allow for excellent regio- and stereochemical control. Palladium(0)-catalyzed amine addition or tosyl carbamate rearrangement gives rise to the γ-substituted phosphonates, whereas, reaction of tosyl carbamates with palladium (II) and base gives oxazolidinones (β-substitution).     

Reaction of ethylN,N-(p-methoxybenzal)-p-aminobenzoate with dialkyl phosphonates

Abstact Interaction of ethylN,N-(p-methoxybenzal)-p-aminobenzoate with dialkyl phosphonates results in dialkyl (N-p-ethoxycarbonylphenylamino)-p-methoxybenzal phosphonates. In the resulting compounds hydrogen bonds are observed by IR spectroscopy.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1301–1303, May, 1996.