Efficient amidation from carboxylic acids and azides via selenocarboxylates: application to the coupling of amino acids and peptides with azides

A facile one-pot procedure for the coupling of carboxylic acid and azide via selenocarboxylate and selenatriazoline has been developed and successfully applied to the coupling of amino acids and peptides with azides. Selenocarboxylates are readily prepared by the reaction of the activated carboxylic acids with LiAlHSeH under mild conditions. The selenocarboxylates formed in situ are used to react directly with azides to form the corresponding amides via a selenatriazoline intermediate. Excellent yields were obtained for electron-deficient azides, and moderate to good yields were obtained for electron-rich azides. The selenocarboxylate/azide amidation reaction is clean and chemoselective. It provides an attractive alternative method to the conventional acylation of amines when an amide bond needs to be formed without going through an amine intermediate.     

Improved solubility and stability of trialkylammonium selenocarboxylate in organic solvents for efficient amidation with azides

Trialkylammonium selenocarboxylate, formed in situ from the reaction of diacyl diselenide with piperidine in the presence of diisopropylethylamine, was found to react readily at room temperature with electron-deficient azides to form amides in excellent yields. The trialkylammonium selenocarboxylate salt formed has good solubility and stability in organic solvents. The enhanced stability allowed mild heating to improve the amidation yields with electron-rich azides.     

A facile approach to phosphonic acid diesters

The symmetric H‐phosphonates of carbohydrate and other compounds were conveniently prepared by direct transesterification of the corresponding monohydroxylic compounds with diphenyl phosphite. The approach has the merits of mild reaction conditions and high yields. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:208–210, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10130     

Conversion of 2(3H)‐furanones into 1,3,4‐oxadiazoles

A series of 2‐phenyl‐5‐alkenyl‐1,3,4‐oxadiazoles were synthesized in high yields from the corresponding dicarbonylhydrazides through cyclodehydration. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:570–574, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10197     

LiClO4 catalyzed mild and efficient method for the synthesis of thiiranes from oxiranes

Oxiranes are efficiently converted to the corresponding thiiranes by potassium thiocyanate in the presence of catalytic amounts of LiClO₄ with excellent yields under mild and nonaqueous conditions. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:97–99, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20376     

Synthesis of novel macrocyclic di‐ and tetralactams containing triazole subunits

The new macrocyclic di‐ and tetralactams 9 , 15 , and 16 were obtained in 16–24% yields by heating the appropriate bis‐amines 7 or 8 with the corresponding bisaldehyde 5 or 14 in refluxing acetic acid under high‐dilution conditions. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:551–559, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10191     

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.     

Synthesis of diaryl thioethers from aryl halides and potassium thiocyanate

An efficient palladium catalyst was synthesized using nicotine, benzyl chloride and palladium chloride. The structure of this catalyst was characterized and it was then used for the synthesis of diaryl sufides. A variety of diaryl thioethers were synthesized under relatively mild reaction conditions. This protocol avoids foul‐smelling thiols via cross‐coupling of aryl halides with potassium thiocyanate and all substrates give the corresponding products in good to excellent yields in the presence of low amounts of the catalyst. Copyright © 2014 John Wiley & Sons, Ltd.     

A facile synthesis of potassium selenocarboxylates and their oxidation with XeF2 to diacyl diselenides: An X‐ray structural analysis of di(4‐methoxybenzoyl) diselenide

Several potassium selenocarboxylates were synthesized in moderate to good yields by the direct reaction of acyl chlorides with potassium selenide. The potassium salts were readily oxidized with XeF₂ to give diacyl diselenides in quantitative yields. The structure of di(4‐methoxybenzoyl) diselenide was established by X‐ray diffraction analysis. Intramolecular interactions between the carbonyl oxygen and the selenium that is connected to the opposite carbonyl group were observed. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 373–379, 1999     

Synthesis and characterization of poly[phenyl(fluoroalkyloxaalkane)silanediyl]s

Monomeric fluoroalkoxyalkyl(phenyl)dichlorosilanes were synthesized with quantitative yields by hydrosilylation of allyl ethers of fluoroalcohols with phenyldichlorosilane with Pt(Ph₃Sb)₂Cl₂ complex as a catalyst. Starting from these monomers, corresponding polysilanes with weight‐average molecular weights of 2–3 × 10⁴ were obtained by the Wurtz reaction. Increasing the CF₂ groups containing two to six monomer units caused the char yields to increase from 3 to 48% at 800 °C in air. The emission characteristics of these polysilanes in a chloroform solution were examined. They had a narrow peak at 344 nm with a small Stokes shift (≈20 nm). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3761–3767, 2003     

1,3,4‐Thia‐ and ‐selenadiazole and 1,2,4‐triazolo[4,3‐a]pyrimidine derivatives from hydrazonoyl halides

1,2,4‐Triazolo[4,3‐a]pyrimidines, thiadiazolines, selenadiazolines, and unsymmetrical azines were synthesized via reactions of a 4‐isopropylbenzoyl bromide 4‐nitrophenylhydrazone with each of potassium thiocyanate, potassium selenocyanate, ethyl 6‐methyl‐4‐[4‐(methylethyl)phenyl]‐2‐methylthio‐3,4‐dihydropyrimidine‐5‐carboxylate, and alkyl carbodithioate. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:421–426, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10156     

Anionic and ionic coordinative polymerization of L-lactide

The potassium naphthalenide complex with 18-crown-6 is able to initiate anionic polymerization of L -lactide at 20°C. This type of anionic initiator does not have to be removed from the polymer as it does not affect metabolic processes. The ionic polymerization of L -lactide with an initiator based on Zn(II) acetyl acetonate, which is fairly stable, has been investigated. It has been found that this process leads to the corresponding polyesters, at high yields. © 1998 John Wiley & Sons, Ltd.     

Silyl enol ethers as protective groups for alkyl 4-halo-3-oxobutanoates in the Arbuzov reaction with triethyl phosphite

Alkyl 4-bromo- and 4-chloro-3-oxobutanoates were protected as silyl enol ethers. The Arbuzov reaction of these new compounds with triethyl phosphite gave the corresponding silyl enol phosphonates in high yield. Facile deprotection of the silyl group with water gave alkyl 4-(diethoxyphosphinyl)-3-oxobutanoates in high yields. Protection of 1-methylethyl 4-bromo-3-oxobutanoate as the enol acetate followed by the subsequent reaction with triethyl phosphite gave the corresponding phosphonate in high yield. Deprotection with potassium 2-propoxide gave 1-methylethyl 4-(diethoxyphosphinyl)-3-oxobutanoate in good yield. © 1997 John Wiley & Sons, Inc.     

Transition‐metal‐catalyzed reactions of 5‐methylene‐2‐oxazolidinone and 5‐methylene‐1,3‐thiazolidine‐2‐thione with isocyanates

5‐Methylene‐2‐oxazolidinone (1) and 5‐methylene‐1,3‐thiazolidine‐2‐thione (4) react with various isocyanates to give the corresponding urethanes 3 and 5 in high yields in the presence of palladium(0) or palladium(II) catalyst under mild reaction conditions. A mechanism is proposed. Copyright © 2003 John Wiley & Sons, Ltd.     

Nickel(II) complex containing N‐(4,5‐dihydrooxazol‐2‐yl)benzamide ligands: highly efficient catalyst for Heck coupling reactions

Heck reaction catalyzed by Ni(II) containing N‐(4,5‐dihydrooxazol‐2‐yl) benzamide has been developed. The coupling of alkenes with aryl iodide or aryl bromide in the presence of potassium carbonate in DMF provides the corresponding products with moderate to good yields. This method possesses obvious advantages such as low‐cost catalyst and simple experimental operation. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and reaction of selenocarbamic acid sodium and potassium salts and organo-germanium, -tin,and -lead esters

Sodium 2 and potassium selenocarbamates 3 were found to be synthesized in moderate to good yields by the reaction of carbamoyl chlorides with sodium and potassium selenides. The salts 2 and 3 reacted with alkyl halides and organo-germanium, -tin, and -lead chlorides to give the corresponding esters 7–9 in good yields.     

Synthesis and chemical modification of hyperbranched polyethers with terminal hydroxy groups by the anionic ring‐opening polymerization of 3‐alkyl‐3‐hydroxymethyl oxetanes

The anionic ring‐opening polymerization of oxetanes containing hydroxyl groups was carried out with potassium tert‐butoxide as an initiator in the presence of 18‐crown‐6‐ether in N‐methylpyrrolidinone at 180 °C; it yielded corresponding multifunctional hyperbranched polymers: poly(3‐ethyl‐3‐hydroxymethyloxetane)s, with number‐average molecular weights of 2200–4100 in 83–95% yields, and poly(3‐methyl‐3‐hydroxymethyloxetane)s, with number‐average molecular weights of 4600–5200 in 70–95% yields. The synthesized poly(3‐ethyl‐3‐hydroxymethyloxetane)s and poly(3‐methyl‐3‐hydroxymethyloxetane)s were hyperbranched polyethers containing an oxetane moiety and many hydroxy groups at the ends. The postpolymerization of poly(3‐ethyl‐3‐hydroxymethyloxetane)s was performed in the presence of potassium tert‐butoxide and 18‐crown‐6‐ether in N‐methylpyrrolidinone at 180 °C; it yielded corresponding polymers with higher molecular weights in good yields. The cationic polymerization of poly(3‐ethyl‐3‐hydroxymethyloxetane) derivatives was carried out with boron trifluoride etherate as an initiator and was followed by alkaline hydrolysis; this yielded a new branched polymer, a poly(hyperbranched polyether), with many pendant hydroxy groups. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3739–3750, 2004     

Synthesis of novel thia‐oxadiazolophanes

The novel thia‐1,3,4‐oxadiazolophanes were synthesized regioselectively from 1,4‐bis(5‐mercapto‐1,3,4‐oxadiazol‐2‐yl)butane and various 1,ω‐dihaloalkanes in presence of potassium hydroxide. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:273–275, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10141     

Synthesis of polyesters with pendant oxetane groups by the chemoselective alternating copolymerization of 3‐ethyl‐3‐(glycidyloxymethyl)oxetane with carboxylic anhydride and its photochemical reaction

The synthesis of polyesters with pendant oxetane groups by the chemoselective alternating copolymerization of 3‐ethyl‐3‐(glycidyloxymethyl)oxetane (EGMO) with carboxylic anhydride and the photochemical reaction of the resulting polymer was examined. The alternating copolymerization of EGMO with phthalic anhydride proceeded chemoselectively with quaternary onium salts under appropriate reaction conditions, and the corresponding soluble polymers with pendant oxetane groups with number‐average molecular weights of 4700–7200 were obtained in 72–87% yields. Furthermore, the photochemical reaction of the resulting polymers was examined with certain photoacid generators in the film state upon UV irradiation, and it was found that the photocrosslinking reaction of the pendant oxetane groups proceeded smoothly to give the insoluble polymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1952–1961, 2003     

Synthesis of tervalent phosphorus esters in biphasic system using potassium phosphate as unique solid base

The synthesis of tervalent phosphorus esters continues to be a significant area of interest, much of it again directed toward the synthesis of phosphite ligands for metal‐catalyzed reactions. Typically, they were obtained through esterification of the corresponding phosphorus chlorides with the appropriate alcohols in the presence of an amine. In this paper, we present a new method for the synthesis of tervalent phosphorus esters, not yet mentioned in the literature, when potassium phosphate, as a unique base, is used in liquid–solid system. Symmetrical and unsymmetrical phosphites were obtained with good yields (65%–80%) using this method. The compounds were characterized by ³¹P NMR spectroscopy. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:360–364, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20438