Isomer series

Aldol reaction of the a-trimethylsilylated enolate 9 with aldehydes provides nearly equal amounts of chromatographically separable ( )- and (Z)-isomers of iron-acyl complexes 11 via silyloxide elimination from the intermedate aldolate 10 (Table 3). This methodology has been the most commonly employed entry to the (Z)-isomer series. 

Cyvin, S.J., Cyvin, B.N., and Brunvoll, J. Enumeration of Benzenoid Chemical Isomers with a Study of Constant-Isomer Series. 166, 65-119 (1993). 

Cyvin SJ, Cyvin BN, Brunvoll J (1993) Enumeration of Benzenoid Chemical Isomers with a Study of Constant-Isomer Series. 166 65-119 Dartyge E, see Fontaine A (1989) 151 179-203 De Cola L, see Balzani V (1990) 158 31-71 Dear K (1993) Cleaning-up Oxidations with Hydrogen Peroxide. 16 de Mendoza J, see Seel C (1995) 175 101-132... 

Another topic of considerable interest concerns the constant-isomer series of benzenoids. Different problems in this connection have recently been taken up by Dias [56-58], who simultaneously managed to extend the data of Stojmenovic et al. [45]. Also in our laboratory some work with these problems is in progress, but the topic does not seem to be mature enough for a review at present. 

Enumeration of Benzenoid Chemical Isomers with a Study of Constant-Isomer Series... 

Benzenoid (chemical) isomers are, in a strict sense, the benzenoid systems compatible with a formula C H, = (n s). The cardinality of C HS, viz. C HS = n, s is the number of isomers pertaining to the particular formula. The generation of benzenoid isomers (aufbau) is treated and some fundamental principles are formulated in this connection. Several propositions are proved for special classes of benzenoids defined in relation to the place of their formulas in the Dias periodic table (for benzenoid hydrocarbons). Constant-isomer series for benzenoids are treated in particular. They are represented by certain C HS formulas for which n s = In Sjl = n2 52 =. .., where (nk sk) pertains to the k times circumscribed C HS isomers. General formulations for the constant-isomer series are reported in two schemes referred to as the Harary-Harborth picture and the Balaban picture. It is demonstrated how the cardinality n s for a constant-isomer series can be split into two parts, and explicit mathematical formulas are given for one of these parts. Computational results are reported for many benzenoid isomers, especially for the constant-isomer series, both collected from literature and original supplements. Most of the new results account for the classifications according to the symmetry groups of the benzenoids and their A values (color excess). 

In the following we shall give a full account of the one-isomer series of benzenoids (defined below), which explain the unities in Eq. (4) and the last equation of (3). 

The enumeration of benzenoid isomers is the subject of another chapter of this monograph series [8]. It contains a comprehensive historical survey and an extensive tabulation of the enumeration results. In the present chapter some advances of the same topic are reported, but to avoid too much overlapping frequent references to the previous chapter [8] are made. Emphasis will presently be laid on the constant-isomer series of benzenoids (defined below), which is a generalization of the one-isomer series. This topic was only mentioned in the concluding remarks of the previous chapter. 

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