Kamleshwar Tiwari

Synthesis of novel fused heterocycle-oxa-aza-phenanthrene and anthracene derivatives via sequential one-pot synthesis in aqueous micellar system

Oxa-aza-phenanthrene and anthracene derivatives which contain a bridgehead nitrogen are synthesized in an aqueous micellar system. The synthetic route is easy and yield is excellent. In this proposed method, solvent, base and surfactant are optimized and the best result was obtained by DBU in water with surfactant CTAB. All synthesized molecules are new. This method is an efficient, viable and sequential one pot synthetic route for the construction of desired product.

A new eco-friendly strategy for the synthesis of novel antimicrobial spiro-oxindole derivatives via supramolecular catalysis

Novel spiro-oxindole derivatives were synthesised by one-pot multicomponent reaction using isatins, urea and 1,3-dicarbonyls. β-Cyclodextrin, an oligosaccharide, catalysed the reaction and can be reused for further reaction after recovery. This developed synthetic route is environmentally benign in which water is used as solvent to produce excellent yields of products. The synthesised compounds were evaluated for their antimicrobial activities against two bacteria and two fungi. All the synthesised spiro-oxindoles exhibit significant antimicrobial activity.

A Novel Synthesis of the Yohimbane Skeleton-Course of the Synthesis of 15,16,17,18,19,20-Hexadehydroyohimbane by Use of Palladium Catalyzed Insertion of Carbon Monoxide

Abstract In the course of our continuing synthetic experiments on benzoquinolizidine2 and indoloquinolizidine alkaloids3, we have recently utilized palladium catalyzed amidation4 for the synthesis of the berbine alkaloids5. In this present paper we wish to report, what we believe is the first successful utilization of the palladium catalyzed amidation for the synthesis of the hexadehydroyohimbane skeleton.

A Novel Synthesis of Berbines1-Synthesis of 2,3-Dimethoxy-10,11-Methylenedioxyberbine by Use of Palladium Catalyzed Insertion of Carbon Monoxide

Abstract Palladium catalyzed amidation has recently been reported for the synthesis of benzolactams2. We wish to report a simple and efficient method for the synthesis of berbines by the Palladium catalyzed insertion of carbon monoxide under mild reaction conditions such as an atmospheric pressure of carbon monoxide at 95° by use of a catalytic amount of Pd(OAc)2 and PPh3 in presence of a tertiary amine. The approach has wider applicability in the berbine synthesis3 as examplified by the synthesis of 2,3-dimethoxy-10,11-methylene-dioxyberbine 7. The bromo-1-benzyl tetrahydroisoquinoline derivative 5 4, the key precursor, was prepared from the known reaction sequence involving an Schotten-Baumann condensation5 and B.N. reaction followed by sodium borohydride reduction.

Synthesis of Imidazo[2,1-b]-1,3,4-thiadiazoles in DABCO as an Efficient and Recyclable Catalyst

Abstract An efficient and general method has been described for the synthesis of imidazo[2,1-b]-1,3,4-thiadiazole by the reaction of 2-aminothiadiazoles with phenacyl bromides in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO). The method is suitable for the synthesis of functionalized imidazothiadiazoles. GRAPHICAL ABSTRACT

A Convenient Synthesis of Sendaverine

Abstract Sendaverine was isolated from Corydalis aurea willd by Manske and it was found to possess a tetrahydro-isoquinoline skeleton1. The structural formula of the alkaloid has been established by the unambiguous synthesis by Kametani2 and Miwako Mori et al.3

A Novel Synthesis of Berbines- Condensation of 2-(3,4-Dimethoxyphenyl) Ethyl Bromide with 1,4-Dihydro-6,7-Dimethoxy-3 (2H) Isoquinolone-Synthesis of (+)-Xylopinine

Abstract Recently we reported an efficient synthesis of the berbine alkaloids3,4 by the use of the bromo esters5 prepared from 3-isochromanones. Now a new general synthetic route to the berbine alkaloids beginning with the condensation of the phenethylbromide 3 and 3-(2H) isoquinolone 2 is being described. The method gains added advantage of placing desired substitution on both rings A and D of the berbine, emerging from the easy availability of the starting compounds. In conclusion, the present results have not only added one more efficient example to more than a dozen successful procedures of the berbine synthesis6 but also offer a potential route to the structurally parallel indoloquinolizidine alkaloids.

A Novel Synthesis of Berbines1-Synthesis of (2, 3) (10, 11)-Bis(methyl en edioxy) berbine by Use of a Lactone2

Abstract Recently we have evolved an efficient synthesis of the tetrahydroisoquinoline alkaloids by the use of a bromoester essentially like 2 derived from lactone3. In connection with our continuing studies on berbines1,4 we now wish to report a novel total synthesis of (2,3) (10,11) -bis(methylenedioxy) berbine by the use of the bromoester 2. The approach (Scheme 1), as we believe, is the first report of the successful utilization of the bromoester 2 for the effective formation of the ring D of the berbines. The key intermediate in this projected work was ethyl 2-bromomethyl-3,4-methylene-dioxyphenylacetate 2 which was prepared readily by

Supramolecular catalysis in the synthesis of polyfunctionalised pyrroles

An efficient sequential one pot three component reaction involving anilines, DEAD/DMAD and glyoxal in aqueous media is reported. The protocol is environmentally benign and provides a new synthetic route to access polyfunctionalised pyrrole derivatives in high yield. The reaction proceeded via supramolecular catalysis.

Triphenylphosphine-Catalyzed, Novel, One-Pot, Multicomponent Synthesis of Functionalized β-Acetamido Carbonyls

Abstract An efficient triphenylphosphine-catalyzed synthesis of β-acetamido carbonyls via multicomponent reaction of aromatic aldehydes, enolizable ketones or β-keto esters, acid chlorides and acetonitrile at room temperature is described. The process is remarkably simple, environmentally benign, and uses Lewis base for the first time in such type of reaction. GRAPHICAL ABSTRACT