The effects of solvent, temperature, time, weight percent of catalyst on the rate and mechanism of cyclization of natural rubber (NR) was studied in toluene and xylene solutions having tin tetra chloride catalyst (SnCl4). Iodometric titration show, with 8% SnCl4 (based on polymer weight) cyclization occurs, leaving 27.4% of the total unsaturation. Infrared spectra of cyclized NR show decreased absorption intensity at 840 and 780 cm-1 which are characteristic bands of the linear polymer and the appearance of absorption band at 890 cm-1 as cycles were formed By using this chemical modification, NR is transformed into a resinous thermoplastic, hard, non rubbery cyclized material with much less unsaturation than the original rubber, which could find commercial applications as adhesives, printing inks, industrial and ship paints.

Hydrogen peroxide/MoO3, as an efficient and clean oxidizing system was used to afford diasteroselective oxidative cyclization of bisnaphthols to spirans in ethanol at 60oC with high yields. Bisnaphthols were prepared by the reaction of a series of aldehydes and 2-naphthol in the presence of a catalytic amount of H3[P(Mo3O10)4].nH2O (HPA) in refluxing dichloromethane.

Using a time-dependent-density functional theory (TD-DFT), Con8guration Interaction Singles (CIS) and Zerner's Intermediate Neglect of Differential Overlap (ZINDO) methods, we have investigated the UV-Visible spectra of one new intramolecular cyclization at before and after intramolecular attack. All structures were optimized at the B3LYP/6-311++G** level while UV-Visible parameters were calculated via different basis sets, 6-31++G**, 6-31+G* and 6-31G*. In the all compounds, with the presence of donors substituted lmax values are greater, when acceptors substituted are smaller, in the TD-DFT and CIS methods. In the CIS and TD-DFT methods, after the cyclization oscillator strength is low i.e. possibility of transmission and transmission intensity is low, because between two aromatic rings, carbonyl groups does not exist. The 3D-surfaces diagrams showed changes of the lmax and energy gap compared with Hammett Para-effect number in the CIS and TDDFT methods, clearly. The calculations were performed using GAUSSIAN 09W suite of programs.