Phosphine-free Suzuki cross-coupling reaction: a mild and selective method for the carbon–carbon bond formation in aqueous tea extract

A mild and selective protocol has been developed for the palladium-catalyzed phosphine-free Suzuki cross-coupling reaction of aryl bromides with arylboronic acids in aqueous tea extract at room temperature. It is noteworthy that the aqueous tea extract plays an important role in the reaction, and various functional groups are tolerated under the optimized conditions. The reactions proceeded with very good chemoselectivity in favor of the bromo instead of the chloro group even at higher temperatures. Furthermore, this protocol could be applied to the cross-coupling of 4-bromoindole without protecting the base sensitive amine group with arylboronic acids in moderate to excellent yields.     

Studies on 2,1-benzisoxazoles. Behaviour towards electrophilic substitution and cycloaddition reactions

The behaviour of 2,1-benzisoxazoles (anthranils) towards electrophilic substitutions has been studied. Nitration of 5-chloro-2,1-benzisoxazole (VII) exclusively gives 4-nitro-5-chloro-2,1-benzisoxazole (XII). However, 5-chloro-3-phenyl-2,1-benzisoxazole (VIII) gives dinitrated products XIII, one nitro group entering at position C₇ instead of C₄ of the carbocyclic ring and the other at the 4′ position of the 3-aryl ring. When 6-nitro-3-carbalkoxy-2,1-benzisoxazoles (X and XI) are nitrated, 4-nitroisomers XV and XVI are obtained exclusively. The substituents already present in the carbocyclic ring exert decisive directing influence. While the parent 2,1-benzisoxazole (Ia) fails to react with dimethyl acetylenedicarboxylate, 6-nitro-2,1-benzisoxazole (XVII) and 5-chloro-2,1-benzisoxazole (VII) react to give 1,4-cycloadducts XIX and XX, respectively. These results suggest that 2,1-benzisoxazoles possess benzenoid as well as ortho-quinonoid character.     

A facile synthesis of 2,4,8,10-tetrahalo-6,12-diaryldibenzo[b,f][1,5]diazocines

3,5-Dihalo-2-aminobenzophenones 2 on prolonged reflux in dry pyridine gave 2,4,8,10-tetrahalo-6,12- diaryldibenzo[b,f][1,5]diazocines 3 in high yields. Attempted condensation of 2 with glycine ester hydrochloride under identical reaction conditions failed to afford 1,4-benzodiazepines.     

Studies on uracils: synthesis of novel pyrido[2,3-d]pyrimidine oxides via ring transformation of isoxazolo[3,4-d]pyrimidine

The reaction of isoxazolo[3,4-d]pyrimidine 1 and cyanoolefins 2 in the presence of triethylamine (Et₃N) as a catalyst afforded an unprecedented one-pot synthesis of biologically important pyrido[2,3-d]pyrimidine oxides 3 in excellent yields.     

Preparation of a novel 16-DPA-P2S5 adduct and its application as a masked α,β-unsaturated ketone in [4+2]cycloaddition reactions

The reaction of 16-DPA with P₄S₁₀ in refluxing benzene afforded a novel adduct 16-DPA-P₂S₅ instead of the expected thione. The adduct undergoes [4+2]cycloaddition with alkyne dienophiles to afford steroidal (17,16-c)pyrans.     

One-pot sequential multi-component reaction: Synthesis of 3-substituted indoles

Here, we have developed a 3-component one-pot sequential approach to 3-substituted indoles. The main advantages of this process are step economy, reduced waste, and operational simplicity. The method involves in situ generation of 3-indolylalcohols from the reaction of indoles and aldehydes in the presence of base. Further, nucleophilic substitution of 3-indolylalcohols with various nucleophiles affords 3-substituted indole derivatives. The reaction does not requires any hazardous and expensive metal catalyst. In addition, the reaction is carried out in (1:1) ethanol–water which is considered as environmentally benign solvent. On the other hand, nonsequential 3-component reaction results in the formation of unwanted bisindolylmethanes.     

Galois theory over rings of arithmetic power series

Let R be a domain, complete with respect to a norm which defines a non-discrete topology on R. We prove that the quotient field of R is ample, generalizing a theorem of Pop. We then consider the case where R is a ring of arithmetic power series which are holomorphic on the closed disc of radius 0<r<1 around the origin, and apply the above result to prove that the absolute Galois group of the quotient field of R is semi-free. This strengthens a theorem of Harbater, who solved the inverse Galois problem over these fields.     

Zeolite-Hy : A Selective And Efficient Catalyst For The Alcoholyses Of Various Alcohols

An efficient and selective method for the conversion of various alcohols into their corresponding ethers in the presence of zeolite under sorvolytic condition is described. The reaction proceeds efficiently at ambient pressure in high yields.     

Bakers' Yeast–Catalyzed Ring Opening of Benzofuroxans: An Efficient Green Synthesis of Aryl-1,2-diamines

A simple and inexpensive method for the reductive cleavage of N–O bond of benzofuroxans with bakers' yeast under nonfermenting condition in aqueous media was achieved. The procedure gives excellent yields of aryl-1,2-diamines.