Gassman studies

To choose finally between the nonclassical and classical structure of the 7-nor-bornenyl ion Gassman studied the solvolysis of benzoates 220-222. If an intermediate nonclassical ion is formed, the effect of the CHj groups on the solvolysis rate will be cumulative, but if classical ions are in an equilibrium, the effect of the second CH3 group should be much smaller than that of the first. Indeed, the first CH3 group shift the equilibrium between classical ions essentially towards the tertiary ion 223 so the second CHj group produces a weak effect since ions 223 and 224 are very similar. The introduction of the first CHj group increases the solvolysis rate by 13.3, that of the second by 11.1 i.e. the effect is cumulative. 

Numerous important contributions from Gassman, Almlof, and Ghosh include studies of chlorin 73 tautomerism (93JPC10964). Tlie 73a and the 73b forms of H2C have both been observed experimentally (see Section III,A,4), although it is well established that 73a is the predominant tautomer (see Sections III,A and III,A,3). Using a local density functional (LDF) at the MP2/DZP2 level, they calculated the 73a/73b difference to be 39 kJ mol ... 

Extensive studies by Gorman and Gassman have shown that an allyl cation can be a 27r-electron component in a normal electron-demand cationic Diels-Alder reaction and, since a carbocation is a very strong electron-withdrawing group, the allyl cation is a highly reactive dienophile [19a, 21]. 

In marked contrast to the results of Gassman and Schrock, major differences were noted by Casey and co-workers in a series of studies utilizing phenylcarbene-substituted W(0) complexes in reactions with olefins. The H NMR spectra of new phenylcarbene tungsten and iron (69) complexes indicate a substantial positive charge residing on the carbene carbon, and as expected, these complexes readily form ylides on reaction with phosphines ... 

Gassman and Creary besides studying the parent 2-bicyclo[4.1.0]heptyl derivatives 75 and 76, also examined the effects of introducing a 4,5-double bond as in 77 and 78. The relative rates given below were for p-nitrobenzoate hydrolysis in 70% acetone at 100°C, and... 

Since the publication of Haywood-Farmer s comprehensive review which covered the literature in detail up through 1972 and in part into 1973, the solvolyses of a number of additional cyclopropane-containing systems have been studied in which trishomocyclopropenyl cations were implicated or discussed. Thus, Masamune and coworkers and Gassman and Creary " " studied the solvolyses of the exo- and endo-anti-tricyclo[3.1.1.0 ]heptan-6-yl p-nitrobenzoate and tosylate (111 and 112) (Scheme 16). For these two compounds, the exo.endo rate ratio after correcting for different leaving groups and solvents was 56 1. From looking at the products and from consideration of the relative rates of the non-cyclopropanated materials = 10 ) it was proposed... 

Finally, Gassman and Talley studied the effects of a-cyano substitution on the kinetics of solvolysis in 2,2,2-trifluoroethanol of the 8-tricyclo[3.2.1.0 " ]octyl system 123. 

Gassman and coworkers have studied possible cyclopropyl participation in the bicyclo[2.1.0]-2-carbinyl tosylate systems 127 and 128. However, the products were explained in terms of cyclobutane ring bond shifts. 

The authors wish to thank the US Army Research and Development Center for partial support of this study. We also wish to thank Drs J. A. Berson, W. E. Billups, M. Charton, P. Dowd, J. Dyke, S. Farid, R. Fuchs, P. G. Gassman, A. C. Hopkinson, K. D. Jordan, S. G. Lias, R. A. Moss, H. Quast, D. W. Rogers, H. D. Roth, R. D. Topsom, N. J. Turro and D. Van Vechten for unpublished data and for suggestions as to the content and presentation of this chapter. 

There are quite a few comparative studies in this field " and the most extensive ones come from Gassman s groups The effect of the metals on the reactions depicted in equation 102 is presented in Table 2. 

The behaviour of the cation radicals derived from bicyclobutane systems has been under intensive study by Gassman and his coworkers. Currently they have observed that the substituted derivative (185) photorearranges in good yield, using 1-cyanonaphthalene as the electron acceptor, to the isomer (186). Although this product can be synthesized independently by the photocyclization of the diene (187) the authors argue that this route is not in operation. The formation of the product (186) follows the one electron transfer path with subsequent rearrangement within the radical cation (188). ... 

Gassman JJ, Greene T, Wright IT Jr., et al. Design and statistical aspects of the African American Study of Kidney Disease and Hypertension (AASK). J Am Soc Nephrol 2003 14(7 Suppl 2) S 154-165. 

For studies related to the characterization of Ziegle-r—Natta polymerization intermediates with Cp2ZrCl2 as catalyst, see P. Gassman, M. R. 

Cleavage of nonenolizable ketones [1, 923, after citation of ref. 60], In further studies of ketone cleavage, Gassman, Lumb. and Zalar6 found that potassium t-butoxide-water in a 10 3 ratio in aprotic solvents such as DMSO, glyme, hexane, or diethyl ether was the most satisfactory reagent. The last solvent is usually preferred. With most ketones, high yields of acids were obtained after a few hours reaction time at room temperature. 

Thus, in the studied (by Gassman) solvolyses of norbomyl tosylates with oxygen-containing substituents at C the oxygen-containing function has interacted in each... 

A. Ghosh, J. Almlof, and P. G. Gassman, Chem. Phys. Lett., 186,113 (1991). Ab Initio SCF Studies of Basis Set Effects in Free Base Porphin. 

The rearrangement modes of bicyclo[1.1.0]butanes have been described in detail by Hoz PET experiments with bicyclo[1.1.0]butane derivatives were extensively studied by Gassman . 

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