SUM: radical cyclizations

 A few weeks ago I posted a question concering radical cyclization and
 asked what there is anything known of its calculation.
 I have been asked to sum it for the others which is what I am doing with
 I would like to take the chance to say a big 'thank you' to all the
 It was a great help for me.
 The original question was:
 > For the explanation of experimental data I am interested
 > in finding the transition states of radical addition or
 > cyclisation reactions like for example a 6-exo-trig reaction.
 > Is there anyone aware of recent ab-initio or better semi-empirical
 > calculations which revealed the TS of any type of a radical addition
 > or cyclisation?
 These are the answers:
 You might want to look at this paper describing a force-field approach
 to modeling the transitions states of intramolecular cyclization reactions.
 (Spellmeyer and Houk, J. Org. Chem., 1987, 52(6), 959-974.)
 The force-field was optimized to produce minima that looked like the
 transition states of intermolecular radical additions calculated with
 ab initio methods.  The force-field was further optimized to give accurate
 delta-Es for the regio-selectivity and stereo-selectivity observed in
 several intramolecular radical cyclization reactions.
 The accuracy of the model was tested by comparing TSs calculated using ab
 initio methods (UHF/STO-3G was the highest level we could run at the time)
 against the "transition states" we calculated using our force-field.
 They were
 nearly indistinguishable.  These results differed from TSs calculated
 with MINDO/3, and MNDO.
 Beckwith and Schiesser have published a different force-field based on
 intermolecular TSs found using MNDO (Tetrahedron Letts, 1985, 26, 373).
 I hope this gives you a good place to start.  I'd be happy to provide
 more information if you want.
 Good luck,
 David Spellmeyer
 Chiron Coporation
 4560 Horton Street
 Emeryville, CA 94608
 (510)-601-3313 Voice
 (510)-601-3360 FAX
 davids ( ( at ) ) e-mail
 Dear Dr.Loehl,
    I hope the following references on localization of TSs for addition
 reactions of radicals can be of some help. We are currently studying
 structure and reactivity of radical cations, but the kind of TSs on which
 we have long experience are those corresponding to internal migrations and
 abstraction processes. Anyway, if you have any specific question on metho-
 dological aspects, we will be pleased of trying to help you.
 [1] Features of the Potential Energy Surface for Reactions of OH with CH2O
     M.R.Soto and M.Page
     J.Phys.Chem., 1990, 94, 3242
 [2] Computational Study of Addition and Abstraction Reactions between OH
     Radical and Dymethyl Sulfide. A Difficult Case.
     J.Phys.Chem, 1993, 97, 10971
 [3] Computational study of the Addition of OH radical to S=C=S
     Chem.Phys.Lett., 1993, 201, 41
 [4] Radical Addition to HNO.
     M.Page and M.R.Soto
     J.Chem.Phys., 1993, 99, 7709
 [5] Addition of O(3P) to CF3O
     Z.Li and J.S.Francisco
     Chem.Phys.Lett., 1993, 209, 151
 !                                                               !
 !  Laura Coitino                                                !
 !  Universita di Pisa - di Chimica e Chim Industriale    !
 !  Via Risorgimento, 35. I-56100 Pisa, Italy                    !
 !  Phone:  Voice (+39-50)-918204                                !
 !          Fax   (+39-50)-502270                                !
 !  E-mail: laurac ( ( at ) )                        !
 !        : laurac ( ( at ) )                        !
 !                                                               !
 I've been doing computations of TS's for the addition of HO an (3P)O to va-
 rious compounds, mostly by semiempirical methods.  Unfortunately I don't have
 a ref. list handy:  what's been published has been in conjunction with exper-
 iments  (silent discharge plasma decomposition).  I find that Cl-containing
 compounds are quite difficult.  For CHO compounds, the computations are rather
 straightforward:  start from your product, do a reaction coordinate to sepa-
 rate it into reagents, pick the highest energy point to optimize to a transi-
 tion state..... (using keywords like TS in MOPAC--not NEARLY as successful as
 their writeup would have you believe--SIGMA in AMPAC--another tricky one--
 LTRD, POWELL, NLLSQ-also in MOPAC).  Do you have access to Chem Abstracts on-
 line?  If so, it shouldn't be hard to do a literature search....  Let me know
 if you have some more specific questions.  I have a lot of computer time avail-
 able, so could do a bit of trouble-shooting of your inputs.  (Right now I have
 more computer time than my own time, but people have helped me in the past...)
 Irene Newhouse
 It's not a radical reaction, but I published ab initio work on a 6-endo-trig
 reaction in which focussed on the distortion of the TS due to the cycle.  Here
 is the reference:
 C.I.Bayly and F.Grein, "Comparison of an intramolecular Michael-type
 to its intermolecular counterpart: an ab initio theoretical study",
 Journal of Chemistry, vol. 67, pp. 2137-2177 (1989).
 Christopher Bayly
 Best wishes and thank you very much
 |Thorsten Loehl                            Tel.:+49-251/83-3233      |
 |Inst. f. Organische Chemie                Fax :          -9772      |
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