Kinetic and mechanistic study on the thermal reactivity of stabilized phosphorus ylides,part 3: [(Acetyl)(arylcarbamoyl)methylene]triphenylphosphoranes and [(alkoxycarbonyl)(arylcarbamoyl)methylene]triphenylphosphoranes and their thiocarbamoyl analogues

A series of five [(acetyl)(arylcarbabmoyl)methylene]triphenyl‐phosphoranes 1a–e and their thiocarbamoyl analogues 2a–e , [(alkoxycarbonyl)(arylcarbamoyl)methylene]triphenylphosphoranes 3a–e and their thiocarbamoyl analogues 4a–e were prepared and fully characterized. All ylides are found under conditions of flash vacuum pyrolysis to fragment giving arylisocyanate or isothiocyanate and acetyl ylides or alkoxy ylides which undergo thermal extrusion of Ph₃PO. A kinetic study shows that these reactions are unimolecular and are of first‐order nature with no significant substituent effect. The thiocarbamoyl ylides 2 react from 4.6 to 42 times faster than their carbamoyl ylides 1 , while the thiocarbamoyl ylides 4 react from 6.6 to 20.9 times faster than their carbamoyl ylides 3 . © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 39: 6–16, 2007     

Synthesis,thermal reactivity,and kinetics of stabilized phosphorus ylides,part 2: [(Arylcarbamoyl)(cyano)methylene]triphenylphosphoranes and their thiocarbamoyl analogues

A series of five cyano(arylcarbamoyl) phosphorus ylides 2 and five cyano(arylthiocarbamoyl) phosphorus ylides 3 are prepared and fully characterized. Pyrolytic reaction products of a representative example of each type obtained by flash vacuum pyrolysis technique show that they undergo thermal extrusion of Ph₃PO or Ph₃PS. Kinetic study of the gas‐phase pyrolysis of each ylide by static method shows that these reactions are unimolecular and first order with no significant substituent effect, but the thiocarbamoyl ylides 3 react 40–65 times more rapidly than their carbamoyl analogues 2 . © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 496–502, 2006     

Copper-catalyzed tandem reaction of 2-haloanilines with thiocarbamoyl chloride: Synthesis of 2-aminobenzothiazoles

A simple and efficient protocol for the synthesis of 2-aminobenzothiazoles by a ligand-free copper-catalyzed tandem reaction has been developed. In the presence of CuBr and t-BuOK, a variety of 2-haloanilines (halogen?=?Br, I) underwent the reaction with thiocarbamoyl chloride efficiently to afford the corresponding 2-aminobenzothiazoles in good yields (83–94%). The features of this method include good yield, cheap catalyst, mild reaction conditions, and broad substrate scope, which make the protocol practical and attractive in the preparation of some potential pharmaceutically active compounds.     

Synthesis and photophysical properties of benzo[c]thiophene,p-phenylene-, triphenylamine-, and pyrene-based vinylenes

An efficient synthesis of benzo[c]thiophenyl/p-phenylenyl/pyrenyl phosphonate esters has been achieved using ZnBr₂-catalyzed Michaelis–Arbuzov reaction of corresponding benzyl alcohol/bromides at room temperature. Horner–Wadsworth–Emmons reaction of the phosphonate esters with aryl/heteroaryl aldehydes in the presence of t-BuOK furnished the vinylenes in good yields. The absorption and emission characteristics of the synthesized vinylenes were also reported.     

Direct conversion of secondary phosphine oxides and H‐phosphinates with [Di(acyloxy)iodo]benzenes to phosphinic and phosphonic amides

The reaction of [di(acyloxy)iodo]benzene with secondary phosphine oxides or H‐phosphinates in the presence of primary or secondary amines allows one to obtain phosphinic or phosphonic acids amides in the one‐pot process. We take advantage of the strong acylating system DAIB/R₂P(O)H to phosphinylation of amines. However, the reaction mechanism is multipathway and causes yields of phosphinic or phosphonic acids amides to be moderate. When the concentration of amines is low, the intermolecular process plays a main role leading to the formation of carboxylic amides through mixed phosphoric–carboxylic anhydride, and also in the low concentration of amines, tetrahydrofuran effectively competes with the amines in the nucleophilic attack on the acylating intermediates. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:81–86, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20514     

Microwave Michaelis–Becker synthesis of diethyl phosphonates,tetraethyl diphosphonates,and their total or partial dealkylation

Diethyl phosphonates and tetraethyl alkyldiphosphonates were efficiently and rapidly prepared via the Michaelis–Becker reaction, under microwave irradiation. These compounds were then hydrolyzed to phosphonic and diphosphonic acids or selectively monodealkylated to give monoesters of phosphonic acids and symmetrical diethyl esters of diphosphonic acids. These reactions were also achieved rapidly in satisfactory yields with microwave methodology. This methodology was applied with success to the functionalization of a polymer resin. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:369–377, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20561     

Efficient Protocol for Stereoselective Epoxidation of Cinnamic Esters Using TsNBr2

An efficient method has been developed for the synthesis of epoxide from cinnamic esters without any catalyst. The reaction was performed in CH₃CN–water (4:1) using N,N-dibromo-p-toluenesulfonamide (TsNBr₂) in alkaline conditions. This procedure can be utilized for stereoselective synthesis of epoxides from cinnamic esters in excellent yield in a shorter reaction time with exclusive formation of the trans-isomer. The method was further extended successfully for styrenes.     

Alkali Metal and Trimethylsilyl Carbamoselenothioates – Synthesis,Structure, and some Reactions

This paper describes the synthesis and some reactions of potassium, rubidium, cesium and trimethylsilyl carbamoselenothioates. The potassium salts were synthesized in 70–80 % yields by reacting the corresponding thiocarbamoyl chlorides with potassium selenide in acetonitrile. Furthermore, the rubidium and cesium salts were obtained in good yields by treating the trimethylsilyl esters with the corresponding metal fluorides. The crystal structure of acetonitrile‐solvated potassium N,N‐dimethylcarbamoselenothioate consisted of dimeric units, featuring μ‐carbamoselenothioate anions associated with potassium cations that are located on the upper and lower sides of a plane involving two opposing carbamoselenothioate groups. These heavier alkali metal salts readily reacted with alkyl halides to give both S‐ and Se‐alkyl esters. The reaction of the potassium salts with trimethylsilyl chlorides forms S‐ and Se‐trimethylsilyl carbamoselenothioates which are in equilibrium. The reaction of the salts and silyl esters with organo Group‐14 and ‐15 elements halides gave exclusively the corresponding Se‐substituted products in good yields.     

Catalytic Asymmetric Epoxidation of α,β‐Unsaturated Esters with Chiral Yttrium–Biaryldiol Complexes

The full details of the asymmetric epoxidation of α,β‐unsaturated esters catalyzed by yttrium complexes with biaryldiol ligands are described. An yttrium–biphenyldiol catalyst, generated from Y(OiPr)₃–biphenyldiol ligand–triphenylarsine oxide (1:1:1), is suitable for the epoxidation of various α,β‐unsaturated esters. With this catalyst, β‐aryl α,β‐unsaturated esters gave high enantioselectivities and good yields (≤99 % ee). The reactivity of this catalyst is good, and the catalyst loading could be decreased to as little as 0.5–2 mol % (the turnover number was up to 116), while high enantiomeric excesses were maintained. For β‐alkyl α,β‐unsaturated esters, an yttrium–binol catalyst, generated from Y(OiPr)₃–binol ligand–triphenylphosphine oxide (1:1:2), gave the best enantioselectivities (≤97 % ee). The utility of the epoxidation reaction was demonstrated in an efficient synthesis of (?)‐ragaglitazar, a potential antidiabetes agent.     

Convenient synthesis of symmetrical diketosulfides from enolizable ketones using [hydroxy(tosyloxy)iodo]benzene and na2S ⋅ 9H2O

An efficient method for the preparation of symmetrical diketosulfides of the type ArCOCH₂SCH₂COAr has been developed from the reaction of [hydroxy(tosyloxy)iodo]benzene with various acetophenones, followed by treatment with Na₂S ⋅ 9H₂O. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:172–176, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20524     

Derivatives of Some 2-Chloroethylphosphonic Acid Esters,with Plant Growth Regulating Activity

Abstract

A method for the synthesis of esters of 2-(dimethylsulfonium)ethylphos-phonic acid and the results of some trials showing the plant growth regulating activity of these compounds are presented. For the synthesis of the mentioned compounds, dimethyl sulphide is reacted with 2-chloroethylphosphonic acid esters; these esters are obtained through the complex[1] of AlCl₃, PCl₃ and 1,2-dichloroethan (1). Using the optimum reaction conditions, very good yields were obtained (96–99%). This complex is reacted with different alcohols to give 2-chloroethylphosphonic acid esters (2) (R?Me, Et, Pr, i-Pr, Bu, i-Bu, Pe). Using the optimum reaction conditions, in the case of methanol the maximum obtained yield was 50%. In the case of the other alcohols, the obtained yields were between 76 and 83%. An exception is i-propanol. whose ester was obtained with low yields and the reaction parameters modification have little influence on the yield. The reaction of the esters with dimethyl sulphide gives, in good yields (between 69 and 79%). esters of 2-(dimethylsulfonium)ethylphosphonic acid (3). substances with plant growth regulating activity.     

Nano-Mgo-Catalyzed One-Pot Synthesis of Phosphonate Ester Functionalized 2-Amino-3-Cyano-4H-Chromene Scaffolds at Room Temperature

Abstract

A facile and efficient protocol for one-pot three-component synthesis of structurally diverse (2-amino-3-cyano-4H-chromen-4-yl)phosphonic acid diethyl esters from the reaction of salicylaldehydes, malononitrile (or ethyl cyanoacetate), and triethylphosphite using basic nanocrystalline MgO as catalyst in aqueous ethanolic medium at room temperature has been developed. Nano-MgO has been prepared using a simple sol-gel approach. Clean reaction profile, easy reusability of MgO nano-catalyst, mild reaction condition, good yields, and practical applicability are the major advantages of the present protocol.     

Facile synthesis of symmetrical 3,3-diarylacrylates by a Heck-Matsuda reaction: an expedient route to biologically active indanones

A simple and straightforward synthesis of symmetrical 3,3-diarylacrylates based on a Heck-Matsuda reaction of arenediazonium salts bearing electron-donating groups with methylacrylates is described. The reaction employs Pd(OAc)₂ as catalyst and goes to completion within 1 h affording the corresponding unsaturated diaryl esters in good to high yields. This method permitted the expeditious and efficient synthesis of the anticancer 3-arylindanone 5 in two operative steps in 43% overall yield.     

Acetylene Phosphonates as Dienophiles: A Route to Carbocyclic and Aromatic Phosphonates and Diphos-Phonates

Abstract

Systematic research of unsaturated phosphonates, started at the end of the sixties, gave rise to a variety of acetylene phosphonic derivatives. The authors worked out two significant routes to these compounds, (1) action of PCl₅ upon some alkynes followed by HCl elimination which gives alkyne dichlorophosphonates. and (2) Arbuzov reaction of P_III esters with halo- and dihaloalkynes which gives different phosphono- and diphosphonoacetylenes. The phosphonic groups are electron-withdrawing, and acetylenephosphon-ates are typical dienophiles in Diels-Alder cycloaddition of diene-donor/dienophile-acceptor type. Phosphonic esters are less active than corresponding dichlorophosphonates, but diphosphonic esters expose high reactivity. Haloethyne- and dialkylaminoethynephosphonates are sufficiently active in the reaction with simple dienes (butadiene, iso-prene, 2,3-dimethylbutadiene and piperylene), but we were not able to introduce alkyl- or arylacetylene phosphonic esters in the cycloaddition.     

Synthesis of o-Carboranyl Containing Esters of Pentavalent Phosphorus Acids

Abstract

A new method for the synthesis of o-carboranyl containing phosphoric, phosphonic and phosphinic acid esters, where the o-carboranil group is in the ester group, has been developed. The propargyl esters of these acids were prapared in two ways: by the reaction of phosphorus acid salts with propargyl chlorid and by interaction of propargyl alcohol with acid chlorides in the presence of Et₃N. The propargyl esters have been converted into carboranyl containing compounds upon treatment with decaborane and dimethyl aniline     

Simultaneous introduction of phosphonic and carboxylic acid functions to hydroxylated macromolecules

Novel diblock and dihydrophilic ionic–nonionic copolymers, having phosphonic and carboxylic functions at the same carbon atom in the repeating units of the ionic block, were prepared. The addition of 2-diethylphosphono-ethyl acrylate (PC) to hydroxyl groups of the polyglycidol block of the poly(ethylene glycol)-b-polyglycidol block copolymer was followed by the dealkylation of phosphonic acid esters and the hydrolysis of carboxylic acid esters. The polymer was characterized by ¹H, ¹³C, and ³¹P NMR. The kinetics of the PC addition and the hydrolysis of the ethyl carboxylate function were also studied, and a simple bimolecular second-order reaction was established. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 432–443, 2004     

One‐pot synthesis of primary 1‐aminophosphonates: Coupling reaction of carbonyl compounds,hexamethyldisilazane, and diethyl phosphite catalyzed by Al(OTf)3

Al(OTf)₃ has been utilized as a new and efficient catalyst for the selective synthesis of primary 1‐aminophosphonates by a one‐pot coupling reaction of various types of aldehydes/ketones, hexamethyldisilazane, and diethyl phosphite under solvent‐free conditions. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:109–115, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20517     

An efficient nonisocyanate route to polyurethanes via thiol‐ene self‐addition

A novel and efficient strategy for the synthesis of nonisocyanate polyurethanes has been developed via thiol–ene self‐photopolymerization. An aliphatic thiol–ene carbamate monomer (allyl(2‐mercaptoethyl)carbamate, AMC) was synthesized by a one‐step synthesis procedure, from cysteamine and allyl chloroformate. The urethane group was therefore incorporated directly into the monomer precursor, avoiding the problems associated to toxic isocyanates. AMC was successfully stabilized with the radical inhibitor pyrogallol (1% wt). In addition, the use of phenyl phosphonic acid as coadditive allowed its stabilization for lower concentrations of pyrogallol (0.1% wt). AMC was directly transformed into thermoplastic polyurethane (TPU) through thiol–ene photopolymerization by UV‐irradiation at 365 nm. The obtained TPU presented semi‐crystalline nature and very high thermal stability (T_5% ～325 °C). It was found that high concentrations of pyrogallol decreased the reaction rate and final conversion of photopolymerization. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3017–3025     

New approaches to the synthesis of diphosphine dioxides and hypophosphoric acid esters

An anion >P–O⁻ has been applied as an efficient synthetic precursor of four coordination compounds of the R₂P(O)–(O)PR₂ type, namely diphosphine dioxides (R = alkyl, aryl) as well as hypophosphoric acid esters (R = alkoxy, aryloxy), in a one‐pot reaction. Furthermore, there were elaborated some mechanistic aspects of the origin of the >P(O)–O–(O)P< anhydride, as a side‐product of the reaction between the anion >P–O⁻ and >P(O)X (X = Cl, Br) electrophiles. Attention is focused on the synthesis of the >P(O)–(O)P< compounds. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:310–316, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20208     

Microwave‐assisted synthesis of the (E)‐α‐methylalkenoate framework from multifunctionalized allylic phosphonium salts

A convenient and general microwave‐assisted method for the synthesis of stereochemically defined α‐methylalkenoic acids and esters from allylic phosphonium salts in a basic aqueous medium is described. A selective preparation of acids or esters was dependent on the base (NaOH or NaHCO₃) employed in the reaction and could be achieved with good to excellent yields under mild conditions in the absence of hydrides and reducing agents. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:179–186, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21001