Classical Versus Nonstatistical
Behavior in the C²-C6/Ene
Cyclization of Enyne-Allenes: Intramolecular
Kinetic Isotope Effects and Radical Clock Reactions

Chandrasekhar Vavilala; Jan W. Bats; Michael Schmittel

doi:10.1055/s-0029-1218799

PAPER

Classical Versus Nonstatistical Behavior in the C^²-C⁶/Ene Cyclization of Enyne-Allenes: Intramolecular Kinetic Isotope Effects and Radical Clock Reactions

Chandrasekhar Vavilala^a,†, Jan W. Bats^b, Michael Schmittel*^a
^a FB 8 (Chemie-Biologie), Universität Siegen, Adolf-Reichwein-Str., 57068 Siegen, Germany
^b Institut für Organische Chemie und Chemische Biologie, Johann Wolfgang Goethe-Universität, Max-von-Laue-Str. 7, 60438 Frankfurt am Main, Germany
Fax: +49(271)7403270; e-Mail: schmittel@chemie.uni-siegen.de;

Abstract

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Abstract

The effects of aryl groups on the mechanism of the C^²-C⁶/ene cyclization of enyne-allenes were studied by means of radical clock openings and intramolecular kinetic isotope effects. Upon attachment of a single aryl group at either the alkyne or the allene terminus, the thermal reaction proceeds by a stepwise mechanism that shows significant nonstatistical dynamic effects. Despite this, we were able to intercept the intermediate diradical intramolecularly by using the ultrafast diphenylcyclopropyl radical clock reaction. When aryl groups were present at both the alkyne and allene termini, the intramolecular kinetic isotope effects were consistent with a classical stepwise mechanism. The present study thus demonstrates the shift in reaction mechanism from a nonstatistical stepwise mechanism to a classical stepwise behavior, depending on the substituents.

Key words

ene reactions - allenes - alkynes - radical reactions - ring closure - kinetic isotope effects

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References

1a Carpenter BK. Determination of Organic Reaction Mechanisms Wiley; New York: 1984.

1b Reactive Intermediate Chemistry Moss RA. Platz MS. Jones M. Wiley; Hoboken: 2004.

2a Carpenter BK. Acc. Chem. Res. 1992, 25: 520

2b Carpenter BK. Angew. Chem. Int. Ed. 1998, 37: 3340

2c Hrovat DA. Duncan JA. Borden WT. J. Am. Chem. Soc. 1999, 121: 169

2d Reyes MB. Carpenter BK.
J. Am. Chem. Soc. 2000, 122: 10163

2e Debbert SL. Carpenter BK. Hrovat DA. Borden WT. J. Am. Chem. Soc. 2002, 124: 7896

2f Carpenter BK. J. Phys. Org. Chem. 2003, 16: 858

For some recent reviews on nonstatistical dynamic effects with citations to the relevant literature, see:

3a Carpenter BK. In Reactive Intermediate Chemistry Moss RA. Platz MS. Jones M. Wiley-Interscience; Hoboken / NJ: 2004. p.925

3b Ess DH. Wheeler SE. Iafe RG. Xu L. Çelebi-Ölçüm N. Houk KN. Angew. Chem. Int. Ed. 2008, 47: 7592

3c Yamataka H. Adv. Phys. Org. Chem. 2010, 44: 173

4 Schmittel M. Strittmatter M. Kiau S. Tetrahedron Lett. 1995, 36: 4975

5a Myers AG. Kuo EY. Finney NS. J. Am. Chem. Soc. 1989, 111: 8057

5b Nagata R. Yamanaka H. Okazaki E. Saito I. Tetrahedron Lett. 1989, 30: 4995

6a Schmittel M. Strittmatter M. Kiau S. Angew. Chem., Int. Ed. Engl. 1996, 35: 1843

6b Schmittel M. Strittmatter M. Vollmann K. Kiau S. Tetrahedron Lett. 1996, 37: 999

6c Schmittel M. Steffen JP. Auer D. Maywald M. Tetrahedron Lett. 1997, 38: 6177

6d Schmittel M. Keller M. Kiau S. Strittmatter M. Chem. Eur. J. 1997, 3: 807

6e Engels B. Lennartz C. Hanrath M. Schmittel M. Strittmatter M. Angew. Chem. Int. Ed. 1998, 37: 1960

6f Schmittel M. Strittmatter M. Tetrahedron 1998, 54: 13751

6g Li H.-B. Zhang H.-R. Petersen JL. Wang KK. J. Org. Chem. 2001, 66: 6662

6h Schmittel M. Steffen J.-P. Maywald M. Engels B. Helten H. Musch P. J. Chem. Soc., Perkin Trans. 2 2001, 1331

6i Yang YH. Petersen JL. Wang KK. J. Org. Chem. 2003, 68: 5832

6j Yang YH. Petersen JL. Wang KK. J. Org. Chem. 2003, 68: 8545

7a Engels B. Hanrath M. J. Am. Chem. Soc. 1998, 120: 6356

7b Schreiner PR. Prall M. J. Am. Chem. Soc. 1999, 121: 8615

7c Cramer CJ. Kormos BL. Seierstad M. Sherer EC. Winget P. Org. Lett. 2001, 3: 1881

7d de Visser SP. Filatov M. Shaik S. Phys. Chem. Chem. Phys. 2001, 3: 1242

7e Stahl F. Moran D. Schleyer PV. Prall M. Schreiner PR. J. Org. Chem. 2002, 67: 1453

7f Schreiner PR. Navarro-Vázquez A. Prall M. Acc. Chem. Res. 2005, 38: 29

8a Zhang H.-R. Wang KK. J. Org. Chem. 1999, 64: 7996

8b Wang KK. Zhang H.-R. Petersen JL. J. Org. Chem. 1999, 64: 1650

8c Dai W.-X. Petersen JL. Wang KK. Org. Lett. 2006, 8: 4665

8d Zhang Y.-Z. Petersen JL. Wang KK. Org. Lett. 2007, 9: 1025

9a Schmittel M. Kiau S. Siebert T. Strittmatter M. Tetrahedron Lett. 1996, 37: 7691

9b Schmittel M. Maywald M. Strittmatter M. Synlett 1997, 165

10 Musch PW. Engels B. J. Am. Chem. Soc. 2001, 123: 5557

11 Schmittel M. Vavilala C. J. Org. Chem. 2005, 70: 4865

12 Bekele T. Christian CF. Lipton MA. Singleton DA. J. Am. Chem. Soc. 2005, 127: 9216

13 Schmittel M. Vavilala C. Jaquet R. Angew. Chem. Int. Ed. 2007, 46: 6911

14 Schmittel M. Mahajan AA. Bucher G. Bats JW.
J. Org. Chem. 2007, 72: 2166

15 Roensch KR. Larock RC. J. Org. Chem. 2002, 67: 86

16 Schmittel M. Strittmatter M. Schenk WA. Hagel M. Z. Naturforsch., B 1998, 53: 1015

17 Borzilleri RM. Weinreb SM. Parvez M. J. Am. Chem. Soc. 1994, 116: 9789

18 Macdonald TL. Reagan DR. Brinkmeyer RS. J. Org. Chem. 1980, 45: 4740

19a Starflinger W. Kresze G. Huss K. J. Org. Chem. 1986, 51: 37

19b Orfanopoulos M. Foote CS. J. Am. Chem. Soc. 1988, 110: 6583

19c Orfanopoulos M. Smonou I. Foote CS. J. Am. Chem. Soc. 1990, 112: 3607

19d Song Z. Beak P. J. Am. Chem. Soc. 1990, 112: 8126

19e Adam W. Krebs O. Orfanopoulos M. Stratakis M. Vougioukalakis GC. J. Org. Chem. 2003, 68: 2420

20 Guan X. Phillips DL. THEOCHEM 2007, 811: 135

21 Schmittel M. Kiau S. Liebigs Ann./Recl. 1997, 733

22 Kawano T. Suehiro M. Ueda I. Chem. Lett. 2006, 35: 58

23a Ohno K. Takagi Y. Matsuura H. J. Phys. Chem. 1993, 97: 5530

23b Weiske T. Schwarz H. Chem. Ber. 1983, 116: 324

24 Sheldrick GM. Acta Crystallogr., Sect. A 2008, 64: 112

Classical Versus Nonstatistical Behavior in the C²-C6/Ene Cyclization of Enyne-Allenes: Intramolecular Kinetic Isotope Effects and Radical Clock Reactions

Classical Versus Nonstatistical Behavior in the C^²-C⁶/Ene Cyclization of Enyne-Allenes: Intramolecular Kinetic Isotope Effects and Radical Clock Reactions