Rama Rao Tata

CH Activation in S-Alkenyl Sulfoximines: An Endo 1,5-Hydrogen Migration†

Intramolecular redox reaction: heating N-alkyl, N-allyl-, and N-benzyl-substituted S-alkenyl sulfoximines under appropriate conditions results in the formation of NH-S-alkyl sulfoximines. The intramolecular redox reaction involves a hydride transfer that occurs by a 6-endo-trig process. The intermediates in the reaction can also give access to four- and six-membered heterocyclic rings and a new class of chiral dienes.

Catalytic Generation of Vinylthionium Ions. (4 + 3)-Cycloadditions and Friedel–Crafts Alkylations

A 3-phenylsulfanyl-substituted allylic alcohol and an ester thereof were treated with Brønsted acids or a gold catalyst, respectively, to generate vinylthionium ions. These species react with dienes, primarily substituted furans, to give products of either (4 + 3)-cycloaddition or Friedel-Crafts alkylation. The results are rationalized on the basis of a stepwise mechanism in which the relative rates of ring closure versus proton loss in the intermediate σ-complex determine the course of the reaction.

Controlled Ion Release from Novel Polyester/Ceramic Composites Enhances Osteoinductivity

Due to the growing number of patients suffering from musculoskeletal defects and the limited supply of and sub-optimal outcomes associated with biological graft materials, novel biomaterials must be created that can function as graft substitutes. For bone regeneration, composite materials that mimic the organic and inorganic phases of natural bone can provide cues which expedite and enhance endogenous repair. Specifically, recent research has shown that calcium and phosphate ions are inherently osteoinductive, so controllably delivering their release holds significant promise for this field. In this study, unique aliphatic polyesters were synthesized and complexed with a rapidly decomposing ceramic (monobasic calcium phosphate, MCP) yielding novel polymer/ceramic composite biomaterials. It was discovered that the fast dissolution and rapid burst release of ions from MCP could be modulated depending on polymer length and chemistry. Also, controlled ion release was found to moderate solution pH associated with polyester degradation. When composite biomaterials were incubated with mesenchymal stems cells (MSCs) they were found to better facilitate osteogenic differentiation than the individual components as evidenced by increased alkaline phosphate expression and more rapid mineralization. These results indicate that controlling calcium and phosphate ion release via a polyester matrix is a promising approach for bone regenerative engineering.

Synthesis of 3-(Arylsulfonyl)-3-pyrrolines from Allenyl Sulfonamides by Silver Ion Catalysis

Treatment of allenyl sulfonamides with catalytic amounts of silver fluoride in acetonitrile at reflux afforded the corresponding 3-sulfonyl-3-pyrrolines in excellent yields by intramolecular hydroamination via a 5- endo-trig cyclization. The starting allenyl sulfonamides were prepared by lithiation of allenic sulfones and trapping with various N-sulfonylimines.