P-Dienes

The constants in Eqs. XVII-88-XVI1-90 may be calculated fiom theory to give the Henry s law constant K from Eq. XVII-87, the experimental n /P dien gives the surface area. Alternatively, the constants may be arrived at from an experimental K (assuming that A is known) and either the isosteric heat of adsorption... 

Gawronsky and Gawronska35 observed this ambiguity and studied the case represented in Figure 7(b), analysing the following compounds, all characterized by P diene helicity. 

P. Knolle, H. Lohr, U. Treichel, H. P. Dienes, A. Lohse, J. Schlaack, and G. Gerken, Parenchymal and nonparenchymal liver cells and their interaction in the local immune response, Z. Gastroenterol. 33 613-620 (1995). 

The attacking electrophile E + first interacts with Fe atom to give a p diene cationic intermediate which then loses a proton to give the final product, as shown... 

Steindl P, Ferenci P, Dienes HP, Grimm G, Pabinger I, Madl C et al. Wilson s disease in patients presenting with liver disease a diagnostic challenge. Gastroenterology 1997 113 212-8. 

The facial selectivity observed with the P dienes could be explained by an approach of the dienophile from the top side of the more stable extended conformation 2P(ext) in which a 1,3-diaxial interaction with the 0-C5 bond is avoided (Figure 1). TTiis selectivity was also observed by Stoodley et al, in a similar case (13). For the same reasons, in the case of the a-dienes 2a and 8a, the major approach comes from the bottom side (from the side of OH-2) which now corresponds to the si face of the extended form 2a(ext) as depicted in Figure 2. These assumptions were supported using the partially protected dienes 3-5 a and p as shown below. 

Figure 1. Approach of dienophiles to the preferred extended conformation of p-dienes.

Besides the Wilkinson complex, [(diene)RhCl]2 (diene = 1,5-cycIooctadiene, norbomadiene, etc.), [Rh(P-P)(diene)] X (X = Bp4, C104 , PF, P-P = bisphosphine) and Rh6(CO)i6 of a cluster complex, are used as rhodium catalysts [64]. The selective hydrogenation of an olefin with a Wilkinson complex is shown in eq. (18.32). The carvone absorbed hydrogen readily and quantitatively to afford dihydrocarvone in high yield [64]. 

Koblik, A.V., Muradyan, L.A., Dubonosov, A.D., and Zolotovskova, G.P., Diene synthesis with 4-phenylethynylpyrylium salts, Khim. Geterotsikl. Soedin. (Russ.), 307-311, 1990. 

Shusherina, N.P., Diene synthesis with 2-pyrones and 2-pyridones, Russ. Chem. Rev., 43,851,1974 Afarinkia, K., Vinader, V., Nelson, T.D. and Posner, G.H., Diels-Alder cycloadditions of 2-pyrones and 2-pyridones, Tetrahedron, 48, 9111,1992. 

Obviously if all pairs are synchronized in T , T2 then by unification of T-j. To and erasing all fictitious entities we obtain T a feasible solution for the original problem P. Otherwise this task consists in making some local modifications inT , T2 in order to synchronize all pairs and then in finding (in the same way as before) a feasible solution for the original problem. The technique we use to synchronize all pairs is presented in [5]. In the same paper we show that the solution T we obtain for the original problem by synchronization is obtained in a polynomial time. Furthermore if T is an optimal solution of P dien T verifies ... 

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