A Novel Tandem Reaction for the Synthesis of Thieno[2,3-C] Pyrazole

Instudyonnewpharmaceuticalsandagrochemicals,theapplicationofheterocyclesisaveryimportantmethod,whichcanimprovethebiologicalactivities.Intheseyears.moreandmorenewagrochemicalshavebeensynthesizedwhichhavethestructurescontainingheterocycles.especiallypy...     

Synthesis of spiropyrrolidines: 1,3‐dipolar cycloaddition reactions of an azomethine ylide to unusual dipolarophiles; a molecular orbital study of the cycloaddition reaction

A simple and efficient method for the synthesis of novel spiropyrrolidines has been accomplished by regioselective 1,3‐dipolar cycloaddition reactions of an azomethine ylide generated by thermal‐ring opening of cis‐1‐cyclohexyl‐2‐phenyl‐3‐benzoyl aziridine with various (E)‐3‐arylidene‐4‐chromanones. The synthesis proceeds in good yield to afford novel spiropyrrolidines, 1‐cyclohexyl‐2‐phenyl‐3‐aryl‐5‐benzoylpyrrolidine‐spiro‐[4.3′]4′‐chromanones. The X‐ray crystal structure analysis of one of the products confirms its structure. Molecular orbital calculations were performed to investigate the regioselectivity of the cycloaddition process. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 500–507, 1999     

Synthesis of six‐membered silaheterocycles by the ring enlargement of 1,1‐diphenyl‐1‐silacyclopent‐3‐ene

Silabicyclo[3.1.0]hexane 2 obtained from silacyclopent‐3‐ene 1 by dichlorocarbene addition is useful in the synthesis of ring‐expanded products, such as silacyclohexa‐2,4‐diene 3 and 5‐alkoxy‐silacyclohex‐3‐enes 5. Catalytic hydrogenation of compound 3 affords silacyclohexane 4. The new heterocycles are characterized by ¹³C and ¹H NMR, as well as mass spectroscopic data. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 171–175, 1999     

Halogenoarylation of allyl isothiocyanate: Synthesis of 2,5‐disubstituted 2‐thiazolines

A new approach to the synthesis of 2‐R‐5‐benzyl‐2‐thiazolines with the use of chloro‐ and bromoarylation products of allyl isothiocyanate with arenediazonium halides was elaborated. The isothiocyanates obtained were reacted with ammonia, aliphatic or aromatic amines, and sodium methoxide. The use of ammonia or weakly basic amines in this reaction allowed. Intermediate thioureas to be isolated. On the basis of ¹H NMR spectra, amino–imino tautomerism of the synthesized 2,5‐disubstituted 2‐thiazolines were analyzed. 2‐Arylamino‐5‐benzyl‐2‐thiazolines exist mainly in the Z‐configuration of the imino form. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 517–525, 1999     

Utilization of thiazolylacetonitriles in the synthesis of thiophene,thiazole, pyrazolo[1,5‐a]pyrimidine and pyrazolo [5,1‐c]triazine derivatives

Thiazolylcyanothioacetanilides react with α‐haloketones and haloesters to give the corresponding thiophene or thiazole derivatives according to the reaction conditions. Pyrazolo[1,5‐a]pyrimidines and pyrazolo[5,1‐c]triazines were synthesized by reaction of 3‐amino‐4‐(4′‐arylthiazol‐2′‐yl)‐5‐phenylaminopyrazole with different reagents. Structures of the new compounds were confirmed by elemental analyses, spectral data, and alternative methods of synthesis whenever possible. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 508–516, 1999     

Reactivity of nucleoside 5′‐O‐phosphates, ‐phosphorothioates, ‐methanephosphonates,and ‐methanephosphonothioates toward activated xylonucleosides

Alkylation of ambident thymidine 5′‐O‐(O‐alkyl phosphorothioate) anions by means of 3′‐O‐sulfonylated xylothymidine occurs at both O‐ and S‐nucleophilic centers, and formation of an internucleotide bond is accompanied by the process of elimination. Lack of chemoselectivity and low yields of products discriminate against such an approach as an effective method of stereocontrolled synthesis of P‐chiral oligo(nucleoside phosphorothioate)s. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 91–104, 1999     

Chemical Synthesis of Native S‐Palmitoylated Membrane Proteins through Removable‐Backbone‐Modification‐Assisted Ser/Thr Ligation

The preparation of native S‐palmitoylated (S‐palm) membrane proteins is one of the unsolved challenges in chemical protein synthesis. Herein, we report the first chemical synthesis of S‐palm membrane proteins by removable‐backbone‐modification‐assisted Ser/Thr ligation (RBM^GABA‐assisted STL). This method involves two critical steps: 1) synthesis of S‐palm peptides by a new γ‐aminobutyric acid based RBM (RBM^GABA) strategy, and 2) ligation of the S‐palm RBM‐modified peptides to give the desired S‐palm product by the STL method. The utility of the RBM^GABA‐assisted STL method was demonstrated by the synthesis of rabbit S‐palm sarcolipin (SLN) and S‐palm matrix‐2 (M2) ion channel. The synthesis of S‐palm membrane proteins highlights the importance of developing non‐NCL methods for chemical protein synthesis.     

Synthesis and characterization of a [5.5]paracyclophane‐containing silicon by NMR spectroscopy and X‐ray crystallography

The synthesis and characterization of 1,3,10,12‐tetraoxo‐2,11‐(diphenylsilylene)[5.5]par‐acyclophane obtained by reaction of 1,4‐benzenedimethanol and dichlorodiphenylsilane is reported. The structure was established by mass spectrometry; ¹H, ¹³C, and ²⁹Si NMR; and X‐ray diffraction analysis. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 351–354, 1999     

Synthesis of Anomerically Pure,Furanose‐Free α‐Benzyl‐2‐amino‐2‐deoxy‐d‐altro‐ and d‐manno‐pyranosides and Some of Their Derivatives

The anomerically pure benzyl α‐d‐glycoside of 2‐amino‐2‐deoxy‐mannopyranoside was synthesized from d‐glucopyranose via 2‐amino‐2‐deoxy‐d‐altrose intermediates. Unlike the direct synthesis from mannosamine in the literature, our method provides furanose‐free products. A new method for the preparation of cis‐2,3‐oxazolidinones of 2‐amino‐2‐deoxy‐sugars was developed. A selective removal of the glycosidic benzyl group in the presence of 4,6‐O‐benzylidene protection was developed, which may provide new routes for the synthesis of oligosaccharides. Furanose‐free derivatives of α‐benzyl‐2‐amino‐2‐deoxy‐mannopyranuronic acids synthesized here offered possibilities for direct comparisons to prior literature preparations.     

Soluble poly(amide–imide)s prepared by one‐pot solution condensation

A new one‐pot procedure for imide–acid monomer synthesis and polymerization is reported for four new poly(amide–imide)s. Bisphenol A dianhydride (BPADA) was reacted with twice the molar amount of 3‐aminobenzoic acid (3ABA) or 3‐amino‐4‐methylbenzoic acid (3A4MBA) in 1‐methyl‐2‐pyrrolidinone (NMP) and toluene mixture, and the amic acid intermediates cyclized in solution to give two diimide‐containing dicarboxylic acid monomers. Without isolation, the diacid monomers were then polymerized with either 1,3‐diaminomesitylene (DAM) or 1,5‐diaminonaphthalene (1,5NAPda) using triphenyl phosphite‐activation to give a series of four soluble poly(amide–imide)s, PAI. Isolation and purification of the dicarboxylic acid monomers was not necessary for formation of high molecular weight polymers as indicated by intrinsic viscosities of 0.64–1.04 dL/g determined in N,N‐dimethylacetamide (DMAc). All of the PAI were soluble in polar aprotic solvents such as NMP, DMAc, and dimethyl sulfoxide (DMSO). Glass transition temperatures ranged from 243 to 279°C by DSC, and 5% weight loss temperatures were above 400°C in both air and nitrogen. Flexible films cast from DMAc were light yellow, transparent, and tough. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1183–1188, 1999     

Efficient Preparation of the Key Intermediate in Corey's Tamiflu Synthesis

A very efficient two‐step synthesis was developed to prepare the key intermediate in Corey's Tamiflu synthesis. DBU (1,8‐diazabicyclo[5.4.0] undec‐7‐ene) was used as a multifunctional catalyst for a series of reactions in a one pot procedure. The new synthesis was featured by the good availability of the starting material and the ease of the synthetic steps. This method might be practical for large scale preparations.     

Synthetic and spectral studies of novel spiro {bicyclo[3,3,0]octene‐8,3′(2′H)‐indol}‐2′‐ones obtained from indol‐2,3‐diones

The present article reports our approach toward the synthesis of spiro compounds via indol‐2,3‐diones. Thus, reaction of indol‐2,3‐dione derivatives with a secondary cyclic amino acid, namely, (R)‐(−)‐thiazolidine‐4‐carboxylic acid, affords a thiazolo‐oxazolidinone as the main product. When the reaction is carried out in the presence of a dipolarophile, 1,3‐dipolar cycloaddition to the intermediate azomethine ylide leads to a novel spiro compound. The products have been characterized on the basis of spectral studies, and the geometry of the intermediate iminium compound has been optimized by use of the semiempirical molecular orbital method. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 381–384, 1999     

C‐phosphorylation of n‐methylpyrrole

The phosphorylation of N‐methylpyrrole with phosphorus (III) halides has been studied. Migration of the dibromophosphino group from the second to the third position of N‐methylpyrrole, leading to the 3‐dibromophosphine, has been found. Methods for the synthesis of 2,4‐bisphosphorylated pyrroles have been developed. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10:213–221, 1999     

Recent Advances in the Base‐Induced Sommelet–Hauser Rearrangement of Amino Acid Derived Ammonium Ylides

The Sommelet–Hauser rearrangement of N‐benzylic ammonium ylides generated from ammonium salts is an interesting and useful transformation that enables one to convert a readily accessible C–N bond into a new C–C bond to an aromatic ring. The rearrangement was discovered by Sommelet in 1937, studied in detail by Hauser, and applied to organic synthesis by Sato until 1999. Further studies have not advanced because several competitive side reactions and structural limitations of the products severely limit the substrate scope and synthetic applications. In this Personal Account, a history of the research in problem solving and recent advances in the base‐induced Sommelet–Hauser rearrangement are described. This synthetic method developed by my group provides efficient access to various types of α‐aryl‐α‐amino acid and α‐aryl‐β‐amino acid derivatives.     

One‐Pot Synthesis of Hydrophobically Modified Iminosugar C‐Alkynylglycosides: Facile Synthesis of Polyhydroxy Tetrahydroindolizines

A mild and efficient one‐pot method has been developed for the stereoselective synthesis of structurally diverse novel iminosugar C‐alkynylglycosides. The generality of this methodology has been demonstrated with a wide variety of amines and copper acetylides. This one‐pot method has been exploited in the synthesis of new class of DNA cross‐linking agents, polyhydroxy 1‐vinyl‐tetrahydroindolizine derivatives.     

New synthesis of oxindole‐1‐carboxamides

A new synthesis of oxindole‐1‐carboxamides was elaborated by the reaction of oxindole‐1‐phenyl‐carboxylate with various amines. This method also permitted the preparation of N,N‐disubstituted oxindole‐1‐carboxamides.     

Proton transfer‐controlled anionic polymerization of methyl‐substituted β‐lactams with potassium t‐butoxide and subsequent coupling reaction with saccharides

The potassium t‐butoxide‐catalyzed ring‐opening polymerization of 3,3‐dimethyl‐ and 4,4‐dimethyl‐2‐azetidinone proceeds quantitatively in a mixture of N,N‐dimethylacetamide and 5–10 wt % of lithium chloride at 25°C to give the corresponding monodisperse polyamides. The addition of methyl α‐D ‐glucoside into the living polyamide system gives a novel polyamide linked with the glucose moiety at one chain end. A new graft copolymer composed of a water soluble polysaccharide (dextran) backbone and many monodisperse polyamide branches was also prepared by a similar coupling method. The difference in acidity among the lactam monomers, the corresponding polyamides, and the alcohols was essential for the attainment of such a proton transfer‐controlled system composed of the living polymerization and the subsequent coupling reaction. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 909–915, 1999     

Generalized Method for the Production of 1,3‐Benzoxazine, 1,3‐Benzothiazine,and Quinazoline Derivatives from 2‐(Hydroxy,Thio, or Amino) Aromatic Acids Using Triphenylphosphine Thiocyanogen

Abstract

A modified one‐pot method was developed for the synthesis of 1,3‐benzoxazines, in which the preparation of unstable thiocyanogen was omitted. The method was found to be general for substituted (methyl, methoxy, halo, and hydroxy) 2‐hydroxy benzoic acids and 2‐hydroxy naphthoic acids. The method was extended to 2‐thio, 2‐amino, and N‐methyl aminobenzoic acid with which the synthesis of 1,3‐benzothiazine and quinazoline derivatives has been achieved, respectively. It was also found that 3‐hydroxypyridine‐2‐carboxylic acid and 2‐hydroxynicotinic acid using a modified method gave 2‐thioxo‐2,3‐dihydro‐4H‐pyrido[2,3‐e][1,3]oxazin‐4‐one and 2‐thioxo‐2,3‐dihydro‐4H‐pyrido[3,2‐e][1,3]oxazin‐4‐one, respectively. The structures of the new compounds were confirmed by the analysis of their IR, ¹H, and ¹³C NMR spectra.     

New Method of Synthesizing N‐Alkoxycarbonyl‐N‐arylamide with Triphosgene

N‐Chloroformyl‐N‐arylcarbamate, the key intermediate for the synthesis of some excellent pesticides, was synthesized through a new method with triphosgene instead of toxic phosgene. It cannot be obtained through the traditional method using triethylamine as a nucleophile. When triethylamine was replaced by a stronger base, sodium hydride, the product was obtained in good yield.     

AJIPHASE®: A Highly Efficient Synthetic Method for One‐Pot Peptide Elongation in the Solution Phase by an Fmoc Strategy

We previously reported an efficient peptide synthesis method, AJIPHASE®, that comprises repeated reactions and isolations by precipitation. This method utilizes an anchor molecule with long‐chain alkyl groups as a protecting group for the C‐terminus. To further improve this method, we developed a one‐pot synthesis of a peptide sequence wherein the synthetic intermediates were isolated by solvent extraction instead of precipitation. A branched‐chain anchor molecule was used in the new process, significantly enhancing the solubility of long peptides and the operational efficiency compared with the previous method, which employed precipitation for isolation and a straight‐chain aliphatic group. Another prerequisite for this solvent‐extraction‐based strategy was the use of thiomalic acid and DBU for Fmoc deprotection, which facilitates the removal of byproducts, such as the fulvene adduct.