Novel1, 3-Dipolar Cycloaddition Reactions of Acyclic Carbonyl Ylides and Related Chemistry

The thesis entitled novel 1,3-dipolar cycloaddition reactions of acyclic carbonyl ylides and related chemistry embodies the results of the investigations carried out to explore the reactivity of acyclic carbonyl ylides,generated by the reaction of dicarbomethoxy carbine and aldehydes towards dipolarophiles such as activated styrenes,1,2-and 1,4-quinones. In conclusion ,we have explored the reactivity pattern of acyclic carbonyl ylides derived from dicarbomethoxycarbene and aldehyde towards activated styrenes with a view to develop a stereoselective synthesis of highly substituted tetrahydrofuran derivatives. It was also found that the ylide could be trapped by various 1,2-and 1,4-diones to form dioxolane derivatives. It is noteworthy that the cycloaddition is highly region- and stereoselective. With isatins the ylide preferentially adds to the more electrone deficient carbonyl group making it regiospecific. Hetrocyclic compounds are of pivotal importance in organic chemistry, and enormous efforts have been devoted to develop new methodologies for their synthesis. It is noteworthy in this context that, 1,3-dipolar cycloaddition reaction,otherwise called Huisgen reaction, constitutes one of the most efficient methods for the synthesis of five membered heterocycles. Among the various dipoles, carbonyl ylides have received substiancial attention in recent years largely due to their utility in the synthesis of a wide range of oxygen hetrocycles, which are often found as structural subunits of many bioactive natural products.

Studies on the Synthesis and Transformations of a Few 2(3H)- and 3(2H)-Furanones

The thesis entitled studies on the synthesis and transformations of a few 2(3H)- and 3(2H)- furanones. Furanones represent an interesting class of heterocyclic compounds, which constitute the central ring system of many natural products. The derivatives of furan is divided, depending on their structure 2(3H)-furanones(I), 2(5H)-furanones(II), and 3(2H)-furanones(III). Systems I&II are unsatured gama lactones known as ‘butenolides’. Compounds of this type also known as ‘crotonolactones’ based on the parent crotonic acid. In conclusion a number of 2(3H)-and 3(2H)- furanones were synthesized from dibenzoylalkene precursors and were characterized on the basis of spectral analytical and X-ray data. On direct irradiation 3,3-bis(4-chloropheneyl)-5-aryl-3H-furan -2-ones underwent decarbonylation to yield the corresponding alpha, beta- unsaturated carbonyl compounds and upon sensitized irradiation they underwent dimersation arising through a 2+2 cycloaddition reaction. Our studies on 3(2H)-furanones revealed that these compounds are thermally stable, while they undergo extensive decomposition to intractable mixtures under the influence of light. Similarly, the novel dibenzoylalkenes- type systems containing hetroatomatic rings synthesized by us also underwent extensive decomposition under the influence of heat. Some of the 3(2H)-furanones synthesized by us exhibit remarkable anti-proliferative activity.