A side reaction encountered in using the peptide coupling reagent N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ)

An unusual side reaction has been found during an attempt to form an amide link between 2-aminothiazole and thiophene-2-carboxylic acid in the presence of EEDQ. Ethyl N-(-thiazolyl)-carbamate ( 3 ) was isolated in significant amounts indicating that 2-aminothiazole, and perhaps other heterocyclic amines, can react directly with EEDQ to form carbamates.     

Synthesis of tryptanthrin (couroupitine) derivatives by reaction of substituted isatins with phosphoryl chloride

Reaction of 5-methyl-, 5-bromo-, and 5-iodoisatins with phosphoryl chloride gave the corresponding 2,8-disubstituted indolo[2,1-b]quinazoline-6,12-diones in moderate yield. 5,7-Dichloroisatin failed to react with POCl₃. Treatment of an equimolar mixture of isatin and 5-bromoisatin with POCl₃ afforded indolo[2,1-b]-quinazoline-6,12-dione (tryptanthrin), 2,8-dibromoindolo[2,1-b]quinazoline-6,12-dione, and two isomeric monobromo-substituted tryptanthrin derivatives, the 2-bromo isomer prevailing.     

The reaction of lithium trialkylalkynylborate with methanesulphinyl chloride : A novel route to internal acetylenes

Treatment of lithium trialkylalkynylborates (1) with methanesulphinyl chloride gives internal acetylenes (2) in good yields. The reaction proceeds via β-methanesulphinylvinylboranes 3, followed by cis elimination of methanesulphinyl group and dialkylboron groups. The reaction mixture of B-alkyl-9-BBN and 1-lithio-1-heptyne has been treated with methanesulphinyl chloride to provide mainly a cyclooctane derivative 6. This finding is explained in terms of the steric factors in the approach of the methanesulphinyl chloride.     

Triphenyltetrazolium chloride as a new analytical reagent for molybdenum(VI): Application to plant analysis

Solvent extraction of molybdenum(VI) ion associate with triphenyltetrazolium chloride (TTC) has been studied. TTC was proposed as reagent for the spectrophotometric determination of micro amounts of molybdenum(VI) at λ_max 250 nm. The optimum conditions for extraction of molybdenum(VI) as an ionassociation complex with TTC has been determined. Beer’s law is obeyed in the range of 0.5–10 μg/mL molybdenum(VI). The molar absorptivity of the ion-pair is 1 × 10⁶ L/mol cm. The sensitivity of the method is 9.6 × 10⁻⁵ μg/cm². The characteristic values for the extraction equilibrium and the equilibrium in the aqueous phase are: distribution constant K _D = 32.64, extraction constant K _ex = 2.19 × 10¹⁰ association constant β = 6.71 × 10⁸. The interferences of different cations, anions on molybdenum(VI) determination were also investigated. A sensitive and selective method for the determination of microquantities of molybdenum(VI) has been developed. The determination was carried out without preliminary separation of molybdenum. A novel procedure of molybdenum(VI) extraction and spectrophotometric determination in different plant samples was examined.     

A novel reagent (N_succinimidyl diphenylphosphate) for synthesis of active ester and peptide

N-succinimidyl diphenylphosphate (SDPP) was prepared. This reagent was useful for the preparation of active esters and peptides in stead of dicyclohexylcarbodiimide.     

A novel and useful oxidative intramolecular coupling reaction of phenol ether derivatives on treatment with a combination of hypervalent iodine(III) reagent and heteropoly acid

The oxidative intramolecular coupling reaction of phenol ether derivatives (nonphenolic derivatives) on treatment with a novel combination of a hypervalent iodine(III) reagent, phenyliodine bis(trifluoroacetate) (PIFA), and heteropoly acid (HPA) was studied. Biaryl compounds were obtained in excellent yields on treatment of highly substituted phenol ethers. On the other hand, spirodienones were specifically formed when one of the preferred arylic coupling sites was substituted with a methoxy group in the para position.     

A novel and efficient oxidative biaryl coupling reaction of phenol ether derivatives using a combination of hypervalent iodine(III) reagent and heteropoly acid

A novel and efficient oxidative biaryl coupling reaction of phenol ether derivatives using a combination of hypervalent iodine(III) reagent, phenyliodine(III) bis(trifluoroacetate) (PIFA), and heteropoly acid has been developed.     

A novel heterocyclic atom exchange reaction with Lawesson's reagent: a one-pot synthesis of dithiomaltol

A one-pot reaction of maltol with Lawesson's reagent generates dithiomaltol, a thiopyran-4-thione, via an unusual heterocyclic atom exchange (HCAE) reaction; only pyrones with proton or aliphatic substituents undergo the HCAE substitution.     

A new entry to carbocyclic nucleosides: oxidative coupling reaction of cycloalkenylsilanes with a nucleobase mediated by hypervalent iodine reagent

A novel method for synthesizing carbocyclic nucleosides was developed. The new synthesis includes a direct coupling reaction of cycloalkenylsilanes with a silylated nucleobase catalyzed by a hypervalent iodine reagent. By applying the method, a novel carbocyclic cytidine derivative having bis(hydroxymethyl)cyclohexene as a pseudosugar moiety, designed as a potential anti-HIV agent, was successfully synthesized.     

Gadolinium(III) chloride: a novel and an efficient reagent for the synthesis of homoallylic alcohols

Carbonyl compounds efficiently undergo nucleophilic addition reactions with allylstannanes in the presence of GdCl₃·6H₂O in acetonitrile under extremely mild reaction conditions to give the corresponding homoallylic alcohols in excellent yields and with high chemoselectivity.     

A novel palladium-catalyzed coupling of epoxides with allyl bromide mediated by indium(I) chloride: a cascade epoxide rearrangement-carbonyl allylation

A cascade epoxide rearrangement-aldehyde allylation was developed by using a combination of InCl and reusable heterogeneous mesoporous silica supported palladium catalysts.     

A fluorous Mukaiyama coupling reagent for a concise condensation reaction: utility of medium-fluorous strategy

The entire study of condensation reactions using various fluorous Mukaiyama reagents, including a novel medium-fluorous strategy, is described. A Mukaiyama reagent bearing a medium-fluorous content tag, between 40 and 60% fluorine by weight, was prepared and examined in ester and amide-forming condensation reactions. At the end of the reactions, the fluorous pyridone by-product was effectively separated from non-fluorous components by increasing the water content of the crude reaction mixture and subsequent filtration of the precipitate. It is also shown that Mukaiyama reagents bearing a fluorous tag increase the reaction rate considerably when compared to their non-fluorous tagged counterpart. Interestingly, it was observed that the longer the fluorous chain, the higher the activity of the Mukaiyama reagent.     

The reaction of chromyl chloride and O-silylated enolates: a novel regiospecific route to α-hydroxy ketones.

Chromyl chloride reacts regiospecifically with O-silylated enolates to form α-hydroxy ketones.