Thesis on heterocyclic compounds


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This thesis describes the synthesis of different cyclic imines and the exploration of their reactivity with cyclopropenones and 1,3-dipoles,as well as an investigation of the chemistry of the products. The synthesis of biologically and pharmaceutically important heterocyclic natural product analogues, such as the pyrroloazepines, indolizidines and pyrrolizidines has been achieved using a cycloaddition reaction between cyclic imidates and cyclopropenones.

A new route to pyridines has been developed using the generation of a proposed 3-azacyclopentadienone as the key step. Regiospecific Diels-Alder reaction of the intermediate 3-azacyclopentadienone with a styrene is followed by chelotropic extrusion of carbon monoxide and loss of hydrogen to give the pyridine.

Topics in Heterocyclic Chemistry

The process is similar to the well-known process by which benzenes are accessed from cyclopentadienones. The azabicyclo[3.

Using the same methodology 1,3-dipolar cycloaddition of nitrile oxides to 4-arylalkylthioazetines afforded a series of oxadiazabicyclo[3. Cycloaddition reactions of a series of benzodiazepines were also studied. Reactions between such cyclic imines and cyclopropenones and 1,3 dipoles were attempted to produce tricyclic and tetracyclic benzodiazepine analogues. Natural products like a antibiotics e. A large majority of synthetic heterocyclics are being used as anticancer agents, antiepleptics, analgesics, hypnotics, pesticides, weed killers and rodenticides.

Alarge number of heterocyclic compounds are also found to be endowed with central nervous system activity, antifertility activity, antiinflammatory activity etc. Heterocycles therefore hold an intrinsic interest for an organic chemist. The present study deals with intensive investigation of some classes of known physiologically active compounds. The programme of research concentrates mainly on synthesis of some nitrogen and oxygen containing analogs of tetra hydrocannabinols, the active constituents of Cannabis sativa Linn, known for its central nervous system activity and also some nonsteroidal antifertility agents, which can be safely and efficaciously used as oral contraceptives.

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Further a few anthraquinones and flavonoids have been extracted from Cassia ii species subgenus fistula. The present work has been divided into three parts. Part 1 The tranquilizing and hallucinogenic effects of some chemicals have led to believe that it is possible to control behaviour and mood of persons clinically. All these compounds affect the central nervous system CMS. The cannabis prepa rations such as bhang, hashish and marijuana derived from the Indian hemp plant cannabis sativa attracted a lot of attention and their importance is due to their pronounced CNS activity. The cannabis preparations have a unique feature of causing both, CNS stimulation and depression, not exhibited by any other class of drugs.

Cannabis derived drugs are also asso ciated witn analgesic properties, spontaneous changes in human behaviour and altered response to stimuli. Any one of these properties is sufficient to make the drug chemically important, but the multiplicity of activities render it useless. Efforts have been directed towards separation of the unique-tranquilizing and stimulating effect of cannabinoids, by insertion of nitrogen atom at the ring junction of pyran and alicyclic ring of tetrahydrocannabinols.

On the other hand some well known CNS active agents such as tryptamine, serotinin, harmine have a indole nucleus in their structural framework and some synthetic benzimidazoles are also endowed with CNS activity.

Keeping these factors in view, compounds iii having mixed features of cannabinoids ring A and B and that of indoles, benzimidazoles or imidazoles ring C and D have been prepared. In another approach it seems possible to modify the biological properties of tetrahydro cannabinols by the insertion of oxygen atom in the ring C as it provides opportunity of repeating the structural features' of ring A and B i.


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This part of thesis has further been divided into three sections. Section I Synthesis of some oxygen analogs ring C of canna binoids has been carried out. Several 8-methyl,3-hydroxy alkyl-6H- benzofuro [2,3-cJ[l] benzopyrans have been prepa red. The ring C is a five membered oxygen heterocyclic fused with aromatic benzene ring ring D. The alkylation of these pyrans 1 with 2-chloroethyl pyrrolidine hydro chloride in the presence of anhydrous potassium carbonate in dryacetone afforded the corresponding 3- 2-pyroiidinoethylj- ethers which have been converted to hydrochlorides.

Attempts have been directed towardsthe synthesis of 7Hindolo [1,2-c] [1,3] benzoxazines III and 5H-imidazolo [1,2-c] [1,3] benzoxazine IV systems, 2- 2'-hydroxyphenyl indoles and 2- 2'-hydroxyphenyl imidazoles have been prepared as intermediates for the synthesis of III and IV respectively as the second hetero ring B could then easily be constructed by introducing a methylene bridge between the OH and NH groups. Section III Many synthetic benzimidazole derivatives are known to possess potent central nervous system activity.

Therefore, synthesis of some cannabinoid analogs, having mixed features of benzimidazoles and cannabinolds have been carried out. Succesful attempts have been made to prepare 7H-benzimidazolo [l,2-c] [1,3] benzoxazines V and 7H-pyridoimidazolo [l,2-c] [1,3] benzoxazines VJ 2- 2'-hydroxyphenyl benzimi dazoles and 2- 2'-hydroxyphenyl pyridoimidazoles have been prepared as intermediates.

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Synopsis for Ph.d Thesis

V vii The structure of these compounds were confirmed by elemental analysis, mass and nmr sDectra studies. Part II Population explosion can be termed as one of the major problems facing mankind today. For centuries, world's birth and death rate had been in a sort of natural equili brium. The development of antiinfective drugs of various kinds and advances made in the medical science has reduced the effectiveness of death, as a possible means of popula tion control.

This has brought us face to face with scarcity of food, material and energy resources. Not only this, it has also given birth to social evils like unemployment, juvenile delinquency, increased incidence of crime and environmental pollution.

Chem 125. Advanced Organic Chemistry. 2. Spirocyclic, Polycyclic, & Heterocyclic Compounds.

Contraceptives derived from plant and other natural sources have been used by men and women, for thousands of years. An important stimulus to research in the field of antifertility compounds was the successful employment of progestational and progestational-estrogenic steroids in the human female. The role of critical balance of estrogens and progestagens for the maintenance of preg nancy by an interplay of hypothalmic, pituitary and ovarian function is well recognised.

An interference with the level of these hormones could cause termination of pregnancy, has been an attractive basis for the designing and develop ment of oral contraceptives. Inspite of remarkable efficacy Vlll of these steroidal preparations as oral contraceptives, the method Is far from ideal. They are Known to proauce undesirable effects characteristic to natural estrogens and progestations and also their continous use and compli cated administration over major part of the active repro ductive life of woman involves the risk of permanent disturbance of normal harmonal balance.

This has diverted the attention towards search of non-steroidal estrogenic compounds which also possess antifertility activity and have minimized hormonal effects.

Synthesis of fluorinated heterocyclic compounds and study of their interaction with DNA

The synthesis of a number of 6H-benzofuro [1,2-c] [1,3] benzopyranones and 2- l',2'- diphenyl vinyl -l-phenyl benzofurans has been described in this part of the thesis. This part has been divided in two sections. Lately interest has been concentrated in compounds having the triarylethylene pattern in rigid frame work and a large number of 1,2 diphenylindenes, 2,3-diphenyl indoles, 2,3 diphenylbenzofurans etc. During the present studies, a novel system has been developed, in which properly substituted benzofurans have a '1,2-diphenylvinyl' group attached at position 2.

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