Catalysis of Organic..

Rothenberg et al. 269Experimental SectionThe technical details of the descriptor selection algorithms will be publishedelsewhere (7). Libraries and subsets of structure strings were generated using Matlab(26). Geometry optimization (for calculating the 3D descriptors) was performed inHyperchem (27), using the MM+ force field in combination with a conjugategradient optimization method (Polak-Ribiere). Structures were optimized in batchmode using dedicated Hyperchem/Matlab scripts. The 2D descriptors were computedusing Matlab and OptiCat (9), and analyzed with Statistica (28). The 3D QSARparameter were calculated using Codessa (29). We used topological, geometrical andelectrostatic descriptors (the CPU time costs of quantum-chemical andthermodynamic QSAR parameters are too high for such large sets). The PLS modelswere built using the NIPALS algorithm (30), including the intercept. Leave-one-outvalidation was performed for all models. All three figures of merit were predictedsimultaneously. Models with an average R 2 > 0.8 were accepted. The 2D and the 3Dmodels contained 9 components each. The most important variables for the 2Dmodel were the number of H and C atoms. For the 3D model, the most relevantdescriptors were related to electronic charges per surface area.References1. P. W. N. M. van Leeuwen, Homogeneous Catalysis: Understanding the Art,Kluwer Academic Press, Amsterdam, 2004.2. C. P. Casey, J. Chem. Educ., 83, 192 (2006).3. A. Ault, J. Chem. Educ., 79, 572 (2002).4. Another good example is the Metolachlor process, see H.-U. Blaser, Adv. Synth.Catal., 344, 17 (2002).5. G. Li, Chemical Industries (CRC Press), 104, (Catal. Org. React.), 177-184(2005).6. N. D. Jones and B. R. James, Adv. Synth. Catal., 344, 1126 (2002).7. For a description of some of the optimization methods discussed here see J.A. Hageman, J. A. Westerhuis, H.-W. Frühauf and G. Rothenberg, Adv.Synth. Catal., 348, 361 (2006).8. See, for example P. W. N. M. van Leeuwen, P. C. J. Kamer and J. N. H. Reek,Pure Appl. Chem., 71, 1443 (1999).9. F. Clerc, OptiCat - A Combinatorial Optimisation Software. OptiCat is availablefree of charge from the author.10. E. Burello, D. Farrusseng and G. Rothenberg, Adv. Synth. Catal., 346, 1845(2004).11. For a recent review see Y. Jin, Soft Computing, 9, 3 (2005).12. For a discussion on using 2D and 3D descriptors see E. Burello and G.Rothenberg, Adv. Synth. Catal., 347, 1969 (2005).13. E. Burello and G. Rothenberg, Adv. Synth. Catal., 345, 1334 (2003).