BC fragments

Fig. 9.1. Left-hand side Representation of an elastic potential energy surface. It has the general form (6.35) with coupling strength parameter e = 0. In case (a), the equilibrium bond distance in the electronic ground state equals the equilibrium separation of the free BC fragment. The heavy arrows schematically indicate two representative trajectories starting at the respective FC points. Right-hand side The corresponding final state distributions.

The waves i ° and 0 can be calculated on the dividing surface without difficulty for any collision energy E, because the inter-fragment potential for i > s is purely radial. The internal eigenfunctions of the BC fragment, (pa i i y) i constitute an orthonormal basis on dS [60,158]. In this representation, the matrices and of the incoming... 

The quasiclassical (QCl) counterpart of k, k, will depend on the classical frequency of the BC fragment, associated with the initial quasiclassical energy, ... 

The energy distribution in the BC fragment can be obtained directly using either LIF, REMPI, IR emission, or by measuring the kinetic energy of the recoiling atom. The latter approach is particularly favourable when H atoms are formed, for, as we have seen, the H atom will receive most of the kinetic energy. 

Wesdemiotis C, SolakN, Polce MJ, Dabney DE, Chaicharoen K, Katzenmeyer BC. Fragmentation pathways of polymer ions. Mass Spectrom Rev. 2011 30 523-59. 

The diagonal term of the BC fragment can be obtained as previously illustrated, considering that this fragment is the subject of the primary movement dNj while maintaining dN =0 ... 

The last step in completing the equalization of the AIM potentials is the charge transfer between the BC fragment reached to the internal equilibrium and the atom A found in the last state described, by reiterating to another level the relationships in the chemical potentials of the molecular fragments considered ... 

In correspondence with the three methods of building up the steroid skeleton considered in this chapter, the exposition of the material is divided into three sections. The first of them comprises total syntheses from BC fragments with the initial formation of ring A and the second syntheses with the initial formation of ring D. The third section comprises syntheses of steroid compounds from BD fragments. 

A variant in the production of an intermediate in the Robinson synthesis, the tricyclic ABC diketone (18), was developed by Banerjee and co-workers [635, 636] (Scheme 58). The triester (22) was obtained from a-ethoxycarbonylcyclohexanone (21) by the Michael reaction with methyl acrylate, alkaline cleavage, and esterification, and it was then cyclized by Dieckmann s method with subsequent bromination and dehydrogenation to give the unsaturated keto diester (23). The addition of cyanoacetic ester gave compound (26) from which the keto triester (25) was obtained by methylation, acid hydrolysis, and esterification. The latter, by Dieck-mann cyclization and hydrolysis, gave the BC fragment (24). Selective ketalization, reduction, and hydrolysis of the ketal led to the hydroxy-ketone (27). The trans-B/C linkage present in it required the protection... 

Syntheses of tricyclic ABC intermediates have also been carried out by two other methods, in both of which the key stage from the point of view of stereochemistry was the redaction of the aromatic ring C (Scheme 64). The BC fragment (87) used in one of these methods [665-672] was obtained by two routes. One of them started from 1-amino-6-methoxynaphthalene... 

Another method of synthesis [673-675] differs from the preceding one by the preparation of the BC fragment (91), which was effected by the acylation, hydrogenolysis, and cyclization of the dimethyl ether of hydro-... 

Syntheses via BCD Intermediates with a Five-Mem-bered Ring D. These syntheses generally start from 6-methoxy-l-tetralone or its 5-methyl derivative, which are used as the BC fragments. All the methods used in Chapter II for the synthesis of estrogenic hormones from 14-oxa compounds are employed for the construction of ring D. It must be mentioned that some of the intermediates illustrated in Schemes 70 and 71 have also been obtained by syntheses of the BD - C type (cf. Section 3 of this chapter). 

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