Vanadium oxide catalysts with V2O5 loadings ranging from 2 to 12% w/w supported on various modifications of titania have been prepared by the wet impregnation method. The calcined samples were characterized by X-ray diffraction (XRD), electron spin resonance (ESR), oxygen chemisorption, temperatureprogrammed desorption (TPD) of ammonia, and surface area measurements. The catalytic properties were evaluated for ammoxidation of 3-picoline to nicotinonitrile. Dispersion of vanadia was determined by the oxygen chemisorption at 640 K and by the static method on the samples prereduced at the same temperature. Oxygen chemisorption results suggest that vanadium oxide disperses better on TiO2 (anatase) than it is supported on TiO2 (rutile) or TiO2 containing mixture of anatase and rutile. ESR spectra obtained under ambient conditions for the catalysts reduced at 640 K show the presence of V 4+ ions in axial symmetry. The results of XRD and ESR substantiate the findings of oxygen chemisorption. Ammonia TPD results suggest that V2O5 supported on anatase is more acidic than V2O5 supported on TiO2 (rutile) or TiO2 (rutile and anatase). V2O5-supported anatase TiO2 exhibited higher activities for 3-picoline ammoxidation than V2O5/TiO2 (rutile) and V2O5/TiO2 (anatase + rutile). The catalytic properties during ammoxidation are related to the oxygen chemisorption sites. † IICT communication number: 4300.

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Rearrangements of the 2,6-Diaryl-3,7-dioxabicyclo(3.3.0)octane Skeleton. Part 3. Reaction of Gmelinol with BF3-Etherate and N,N-Dimethylaniline.-The title reaction results in unprecedented formation of a bridged compound (II). Its structure is confirmed by spectroscopic means, X-ray analysis, and chemical transformations. Reduction with BF3· OEt2 and HSiEt3 gives the aryltetralin (III). -(WARD, R. S.; PELTER, A.; VENKATESWARLU, R.; KAMAKSHI, C.; LAKSHMI, A.; Tetrahedron 52

The irradiation of some 6-(w-alkenyl)-cyclohex-2-en-l -ones in micelles gave a carbonyl bridged intramolecular photoadduct but the reaction is restricted t o enones tethered t o an alkene by not more than a four-carbon chain.The generally accepted mechanism of enone-alkene photoannelation involves the formation of an exciplexl which collapses to a 1,4-diradical with the initial bond formation at the P-carbon atom of the enone.2 In the intramolecular version3 the rule of five4 governs the regiochemistry whenever the two reaction C=C bonds are separated by not more than three carbon atoms as in non-conjugated dienes. Frost1 and Margarethas have found no preference for the rule of five in the intramolecular photoannelation of some alkylated cyclohex-2-en-1-ones having an ally1 function at C-6. Becker et a1.6 in a recent study gave evidence for the intermediacy of a 1,4-diradical and noted that intramolecular photoannelation is limited to compounds in which the two reactive centres are separated by a chain of lcss than eight carbons.This prompted us to study some 6-(t~-alkenyl)-cyclohex-2en-1-ones with varying chain length separating the two C=C functions; the preliminary results are now reported. The .i . IICT Communication No. 2571.