Alkyltriphenylphosphonium Salts Research Articles

The Synthesis of α-Aminophosphonates via Enantioselective Organocatalytic Reaction of 1-(N-Acylamino)alkylphosphonium Salts with Dimethyl Phosphite.

α-Aminophosphonic acids are phosphorus analogues of α-amino acids. Compounds of this type find numerous applications in medicine and crop protection due to their unique biological activities. A crucial factor in these activities is the configuration of the stereoisomers. Only a few methods of stereoselective transformation of α-amino acids into their phosphorus analogues are known so far and all of them are based on asymmetric induction, thus involving the use of a chiral substrate. In contrast, we have focused our efforts on the development of an effective method for this type of transformation using a racemic mixture of starting N-protected α-amino acids and a chiral catalyst. Herein, a simple and efficient stereoselective organocatalytic α-amidoalkylation of dimethyl phosphite by 1-(N-acylamino)alkyltriphenylphosphonium salts to enantiomerically enriched α-aminophosphonates is reported. Using 5 mol% of chiral quinine- or hydroquinine-derived quaternary ammonium salts provides final products in very good yields up to 98% and with up to 92% ee. The starting phosphonium salts were easily obtained from α-amino acid derivatives by decarboxylative methoxylation and subsequent substitution with triphenylphosphonium tetrafluoroborate. The appropriate self-disproportionation of enantiomers (SDE) test for selected α-aminophosphonate derivatives via achiral flash chromatography was performed to confirm the reliability of the enantioselectivity results that were obtained.

Catalyst-free Mannich-type reaction of 1-(N-acylamino)alkyltriphenylphosphonium salts with silyl enolates

A catalyst-free reaction of 1-(N-acylamino)alkyltriphenylphosphonium tetrafluoroborates with silyl enolates was developed to prepare β-amino carbonyl compounds. The reported method is a useful approach for the preparation of N-protected β-amino esters as well as N-protected β-amino ketones. The starting 1-(N-acylamino)alkyltriphenylphosphonium tetrafluoroborates are readily available from N-protected α-amino acids. Therefore, the presented approach can be considered a new method for the α-homologation of N-protected α-amino acids to prepare β-amino acid derivatives.

From broad-spectrum biocides to quorum sensing disruptors and mussel repellents: antifouling profile of alkyl triphenylphosphonium salts.

‘Onium’ compounds, including ammonium and phosphonium salts, have been employed as antiseptics and disinfectants. These cationic biocides have been incorporated into multiple materials, principally to avoid bacterial attachment. In this work, we selected 20 alkyl-triphenylphosphonium salts, differing mainly in the length and functionalization of their alkyl chains, in fulfilment of two main objectives: 1) to provide a comprehensive evaluation of the antifouling profile of these molecules with relevant marine fouling organisms; and 2) to shed new light on their potential applications, beyond their classic use as broad-spectrum biocides. In this regard, we demonstrate for the first time that these compounds are also able to act as non-toxic quorum sensing disruptors in two different bacterial models (Chromobacterium violaceum and Vibrio harveyi) as well as repellents in the mussel Mytilus galloprovincialis. In addition, their inhibitory activity on a fouling-relevant enzymatic model (tyrosinase) is characterized. An analysis of the structure-activity relationships of these compounds for antifouling purposes is provided, which may result useful in the design of targeted antifouling solutions with these molecules. Altogether, the findings reported herein provide a different perspective on the biological activities of phosphonium compounds that is particularly focused on, but, as the reader will realize, is not limited to their use as antifouling agents.

N-[1-(Benzotriazol-1-yl)alkyl]amides from N-acyl-α-amino acids or N-alkylamides

A variety of N-(1-methoxyalkyl)amides react with benzotriazole in the presence of PPh3·HBF4 and organic bases (Hünig's base, DBU or DABCO) or solid-state-supported bases (SiO2-Pip or IRA-67) in CHCl3 to give N-[1-(benzotriazol-1-yl)alkyl]amides in good yields. The most convenient and efficient procedure for obtaining N-[1-(benzotriazol-1-yl)alkyl]amides consists, however, of the addition of benzotriazole sodium salt to a solution of crude 1-(N-acylamino)alkyltriphenylphosphonium salt, obtained in situ from N-(1-methoxyalkyl)amides and PPh3·HBF4. A combination of these reactions with the recently described electrochemical decarboxylative α-methoxylation of N-acyl-α-amino acids in the presence of SiO2-Pip enables an effective two-pot transformation of N-acyl-α-amino acids to N-[1-(benzotriazol-1-yl)alkyl]amides.

Comparative Studies on the Amidoalkylating Properties of N-(1-Methoxyalkyl)Amides and 1-(N-Acylamino)Alkyltriphenylphosphonium Salts in the Michaelis–Arbuzov-Like Reaction: A New One-Pot Transformation of N-(1-Methoxyalkyl)Amides into Phosphonic or Phosphinic Analogs of N-Acyl-α-Amino Acids

It was demonstrated that N-(1-methoxyalkyl)amides do not react with trimethyl phosphite under neutral or basic conditions. The treatment of N-(1-methoxyalkyl)amides with trialkyl phosphites or dialkyl phosphonites, triphenylphosphonium tetrafluoroborate, and Hünig's base caused immediate formation of the corresponding 1-(N-acylamino)-alkyltriphenylphosphonium tetrafluoroborates, followed by the slow Michaelis–Arbuzov-like reaction of phosphonium salt with phosphites or phosphonites to α-(N-acylamino)-alkanephosphonic or α-(N-acylamino)alkanephosphinic acid esters, respectively. A plausible mechanism of the considered transformations, assuming an equilibrium between N-(1-alkoxyalkyl)amide, triphenylphosphonium tetrafluoroborate, 1-(N-acylamino)alkyltriphenyl-phosphonium salt, N-acylimine, and N-acyliminium salts, is discussed.

Amidoalkylating Properties of 1-(N-Acylamino)Alkyltriphenylphosphonium Salts

Easily accessible 1-(N-acylamino)alkyltriphenylphosphonium salts react smoothly with nitrogen, sulfur, phosphorus and oxygen nucleophiles in the presence of (i-Pr)2EtN to give the expected α-amidoalkylation products, usually in good or very good yields. α-Amidoalkylation of dialkyl malonates or acetylacetates requires the application of a much stronger base (DBU) and gives the best results under the influence of microwave irradiation. α-Amidoalkylation of enamines was carried out successfully in the presence of (i-Pr)2EtN in a microwave reactor. 1-(N-Acylamino)alkyltriphenylphosphonium salts can be considered as new, convenient and effective α-amidoalkylation agents.

N-(1-acyloaminoalkyl)amidinium salts derived from DBU or related bases as reactive intermediates in α-amidoalkylation reactions

N-Acylamino)alkyltriphenylphosphonium salts 4, when treated with DBU, DBN or TBD in CD3CN or MeCN, were transformed immediately into the corresponding 1-(N- acylamino)alkylamidinium or guanidinium salts 5. Salts 5 with a proton at the α-position underwent slow transformation to the corresponding enamides 6. 1-(N- Acylamino)alkyltriphenylphosphonium salts 4, amidinium or guanidinium salts 5, as well as enamides 6 reacted readily with β-dicarbonyl compounds in the presence of corresponding base under microwave irradiation at 60 o C to give the expected product of α-amidoalkylation of the enolate anion. The role of 1-(N-acylamino)alkylamidinium or guanidinium salts 5 as reactive intermediates in α-amidoalkylation with 1-(N-acylamino)alkyltriphenylphosphonium salts is discussed.

α-Amidoalkylating Agents from N-Acyl-α-amino Acids: 1-(N-Acylamino)alkyltriphenylphosphonium Salts

N-Acyl-α-amino acids were efficiently transformed in a two-step procedure into 1-N-(acylamino)alkyltriphenylphosphonium salts, new powerful α-amidoalkylating agents. The effect of the α-amino acid structure, the base used [MeONa or a silica gel-supported piperidine (SiO(2)-Pip)], and the main electrolysis parameters (current density, charge consumption) on the yield and selectivity of the electrochemical decarboxylative α-methoxylation of N-acyl-α-amino acids (Hofer-Moest reaction) was investigated. For most proteinogenic and all studied unproteinogenic α-amino acids, very good results were obtained using a substoichiometric amount of SiO(2)-Pip as the base. Only in the cases of N-acylated cysteine, methionine, and tryptophan, attempts to carry out the Hofer-Moest reaction in the applied conditions failed, probably because of the susceptibility of these α-amino acids to an electrochemical oxidation on the side chain. The methoxy group of N-(1-methoxyalkyl)amides was effectively displaced with the triphenylphosphonium group by dissolving an equimolar amount of N-(1-methoxyalkyl)amide and triphenylphosphonium tetrafluoroborate in CH(2)Cl(2) at room temperature for 30 min, followed by the precipitation of 1-N-(acylamino)alkyltriphenylphosphonium salt with Et(2)O.

Application of Wittig Reaction in Synthesis of Novel Pyridine Dicarboxylic Acid Derivatives with High Ligand Activity

A series of novel conjugated molecules with two pyridine dicarboxylic acid units have been synthesized by a Wittig reaction of corresponding alkyltriphenylphosphonium salts with aromatic aldehydes. The novel pyridine dicarboxylic acid derivatives with high ligand activity were completely characterized from their mass and 1H NMR spectra. The E-configuration of these alkenes was confirmed by infrared spectroscopic data.

Thermogravimetrical investigations of the dealkoxycarbonylation of N-acyl-α-triphenylphosphonioglycinates

Thermogravimetrical experiments revealed that immediately after the endothermic process of the melting of N-acyl-α-triphenylphosphonioglycinates 1, an exothermic demethoxycarbonylation of phosphonioglycinates commenced, accompanied by the release of CO 2. The residues contained the corresponding N-acylaminomethyltriphenylphosphonium salts 2 (18.3–49.5%), methyltriphenylphosphonium salts 7 (21.8–67.9%), and the corresponding 1,2-di( N-acylamino)fumaric acid dimethyl ester 6 (2.1–26.0%). When the reaction was carried out in the presence of Ph 3P and the corresponding triphenylphosphine hydrobromide, hydroiodide, or tetrafluoroborate, N-acyl-α-triphenylphosphoniumglycinate bromides and iodides 1a– f underwent demethoxycarbonylation to form the corresponding N-acylaminomethyltriphenylphosphonium salts 2a– f at 95–130 °C in good to excellent yields (79–100%). On the other hand, tetrafluoroborates 1g– i underwent corresponding reactions at about 170–175 °C to give phosphonium tetrafluoroborates 2g– i in much lower yields (34–67%). Plausible mechanisms of the investigated reaction are discussed. It was also demonstrated that the obtained crude α-( N-acylamino)alkyltriphenylphosphonium salts 2 could be applied as valuable α-amidoalkylating agents in spite of their contamination with inert methyltriphenylphosphonium salts 7.

A Novel Synthesis of 1-Aminoalkanephosphonic Acid Derivatives from 1-(N-Acylamino)- alkyltriphenylphosphonium Salts

Efficient and convenient procedures for the α-amidoalkylation of trialkylphosphites with 1-(N-acylamino)alkyltriphenylphosphonium salts followed by a Michaelis–Arbuzov-type reaction to afford 1-(N-acylamino)alkanephosphonic acid esters have been developed. High yields and simple isolation and purification protocols are the main advantages of this method.

ChemInform Abstract: 1‐(N‐Acylamino)alkyltriphenylphosphonium Salts as Synthetic Equivalents of N‐Acylimines and New Effective α‐Amidoalkylating Agents.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

1-( N-Acylamino)alkyltriphenylphosphonium salts as synthetic equivalents of N-acylimines and new effective α-amidoalkylating agents

1-( N-Acylaminoalkyl)triphenylphosphonium salts 2a–f on reaction with DBU in MeCN are transformed into 1-( N-acylaminoalkyl)amidinium salts 3a–f. Amidinium salts 3d– f with a proton at the β-position undergo slow tautomerization into the corresponding enamides 6d–f. The same 1-( N-acylamino)alkyltriphenylphosphonium salts 2d–f in the presence of Hünig’s base are transformed directly into the corresponding enamides. Phosphonium salts 2, amidinium salts 3, and enamides 6 react with dialkyl malonates in the presence of DBU to give the corresponding amidoalkylation products. α-Amidoalkylation of dialkyl malonates is not observed in the presence of ( i-Pr) 2EtN, yet proceeds well under these conditions with more acidic nucleophiles, for example, phthalimide or benzyl mercaptan.

An expedient synthesis of 5-n-alkylresorcinols and novel 5-n-alkylresorcinol haptens.

The first synthesis of bioactive long alkyl chain 5-n-alkylresorcinols, present in whole grain products, by a novel modification of the Wittig reaction is described. All the main long chain 5-n-alkylresorcinols present in rye and wheat, including C23 and C25 analogues and haptens, which have not been previously prepared, were synthesised. Microwave-promoted reactions of a semi-stabilized ylid and alkanals in water gave good yields in both pressurized and open systems. An alternative microwave-promoted synthesis starting from non-stabilized alkyltriphenylphosphonium salts and 3,5-dimethoxybenzaldehyde worked as well. Aqueous media were suitable for the reactions even if the starting materials were not soluble in water. The 5-n-alkylresorcinols are potential biomarkers of whole grain intake, and the new hapten derivatives of 5-n-alkylresorcinols will open the way for the immunochemical detection techniques of alkylresorcinols.

N-Acyl-α -triphenylphosphonio-α -amino Acids: Synthesis and Decarboxylation to α -(N-Acylamino)alkyltriphenylphosphonium Salts

4-Phosphoranylidene-5(4H)-oxazolones 1 undergo hydrolysis in THF in the presence of HBF 4 at room temperature to give N-acyl-α -triphenyphosphonioglycines 3 (R 2 = H) in very good yields. 4-Alkyl-4-triphenylphosphonio-5(4H)-oxazolones 2 react with water in CH 2 Cl 2 /THF solution without any acidic catalyst at 0–5°C in a few days yielding N-acyl-α -triphenylphosphonio-α -amino acids 3 (R 2 = Me) or α -(N-acylamino)alkyltriphenylphosphonium salts 4 (R 2 = alkyl, other then Me). α -Triphenylphosphonio-α -amino acids 3 upon heating to 105–115°C under reduced pressure (5 mm Hg) or upon treatment with a Hünig base in CH 2 Cl 2 at 20°C undergo decarboxylation to give the corresponding α -(N-acylamino)-alkyltriphenylphosphonium salts 4 , usually in very good yields.

ChemInform Abstract: Effect of Base on Alkyltriphenylphosphonium Salts in Polar Aprotic Solvents.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Effect of base on alkyltriphenylphosphonium salts in polar aprotic solvents

When arylmethyl phosphonium salts are treated with a base (e.g., t-BuOK or NaH) they homocouple to form symmetric 1,2-diarylethenes. In some cases, dilution and (or) use of excess base lead to very high yields of the product. This reaction is solvent sensitive: the reaction occurs only when polar aprotic solvents such as acetonitrile or DMSO are used. Other alkyl phosphonium salts (e.g., ethoxycarbonylmethyltriphenylphosphonium bromide and n-butyltriphenylphosphonium bromide) form a ylid (when an α-carbonyl group is present) or lose a phenyl group to form alkyldiphenylphosphine oxides when treated with the base. Mechanistic investigation of the homocoupling reaction indicates that the reaction proceeds through a ylid that acts as a nucleophile on an unreacted phosphonium salt. The resulting adduct undergoes elimination to form the observed product. The E/Z ratio seems to depend on the amount of the base used and the phosphonium salt involved.Key words: phosphonium salts, homocoupling, 1,2-diarylalkene, Ylids.

Synthesis and decarboxylation of N-acyl-α-triphenylphosphonio-α-amino acids: a new synthesis of α-( N-acylamino)alkyltriphenylphosphonium salts

4-Phosphoranylidene-5(4 H)-oxazolones 1 undergo hydrolysis in THF in the presence of HBF 4 at room temperature to give N-acyl-α-triphenylphosphonioglycines 3 (R 2 = H) in very good yields. 4-Alkyl-4-triphenylphosphonio-5(4 H)-oxazolones 2 react with water in CH 2Cl 2/THF solution without any acidic catalyst at 0–5 °C in a few days yielding N-acyl-α-triphenylphosphonio-α-amino acids 3 (R 2 = Me) or α-( N-acylamino)alkyltriphenylphosphonium salt 4 (R 2 = CH 2OMe). α-Triphenylphosphonio-α-amino acids 3, on heating up to 105–115 °C under reduced pressure (5 mmHg) or on treatment with diisopropylethylamine in CH 2Cl 2 at 20 °C undergo decarboxylation to give the corresponding α-( N-acylamino)alkyltriphenylphosphonium salts 4, usually in very good yields.

A new application of the Mitsunobu reaction in the synthesis of phosphonium salts

The condensation of methanol or primary alcohols with triphenylphosphonium tetrafluoroborate in the presence of ethyl azodicarboxylate and triphenylphosphine in THF at room temperature gives the respective alkyltriphenylphosphonium salts in good yields. The reaction also worked for the conversion of N-acyl-2-hydroxyglycinates into N-acyl-2-triphenylphosphonioglycinates.

ChemInform Abstract: Synthesis and Biological Activity of New Diarylalkenes.

Condensation of 5-nitro-, 3-chloro-, and 5-chlorosalicylic acids with formaldehyde afforded dimeric disalicylmethanes, which were O-methylated with dimethyl sulfate and oxidized with chromium(VI) oxide to diarylketones 9, 10, 11, 12. Wittig reaction with ylides obtained by deprotonation of alkyltriphenylphosphonium salts with sodium bis(trimethylsilyl)amide yielded a series of diarylalkenes. Some of the obtained compounds showed high antibacterial activity in vitro against Erwinia carotovora.