The Conservaon of Orbital Symmetry

J. Am. Chem. Soc. 87, 395 (1965). Angew. Chem. Int. Ed. 8, 781, 1969.

Robert B. Woodward, nobel prize in 1965

Roald Hoffman, nobel prize in 1981 Livros

• Woodward, RB; Hoffmann, R “The Conservaon of Orbital Symmetry”; Academic: New York, 1970. • Fringuelli, F. , Tacchi, A. “Dienes in the Diels-Alder Reacon”, Wiley-Interscience, 1990. • Spino, C. “Some Features of [4+2]- and [2+2]- Cycloaddions” EdUFSCar, São Carlos, 1993. • Carruthers, W."Cycloaddion Reacons in Organic Synthesis", in Tetrahedron Organic Chemistry Series, vol. 8, Pergamon Press, Oxford, UK, 1990. Controvérsias

Impossible Dreams

E. J. Corey Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts

J. Org. Chem. 2004, 69, 2917-2919.

“On May 4, 1964, I suggested to my colleague The Nobel Prize in Chemistry 1990 was R. B. Woodward a simple explanation involving awarded to Elias James Corey "for his the symmetry of the perturbed (HOMO) development of the theory and molecular orbitals for the stereoselective methodology of organic synthesis". cyclobutene 1,3-butadiene and 1,3,5-hexatriene cyclohexadiene conversions that provided the basis for the further development of these ideas into what became known as the Woodward- Hoffmann rules.” The Conservation of Orbital Symmetry

Efeito do substituinte Efeito do substituinte no butadieno

Z = retirador X = doador de e- The Diels-Alder Reacon

The Nobel Prize in Chemistry 1950

Web of Science: 22.684 citações Regioselecvity of [4 + 2] Cycloaddions

• AM1 semi-empirical MO calculaon: Dieno Dienó filo

E HOMO, eV -9.3654 -10.5525

• the diene HOMO and dienophile LUMO are E LUMO, eV 0.4699 1.4384 indeed the pair closer together in energy, HOMO coeff. 1 0.560 10.804 eV compared to 11.022 eV for the alternave. 2 0.432 • Further, the coefficients show us what we 3 0.432 drew in our pictures: the opposite phase 4 0.560 signs at the two termini of both diene and dienophile froner orbitals. LUMO coeff. 1 -0.707 2 0.707 • Electron release in the diene should raise Dieno Dienó filo the energy of its HOMO and LUMO E , eV -9.0589 -10.6945 • Electron withdrawal from the dienophile HOMO should lower the energy of its HOMO and E LUMO, eV 0.4824 -0.1389 LUMO HOMO coeff. 1 0.647 • the HOMO-LUMO gap is now 8.92 eV, 2 0.406 almost 1 eV less. In fact, the reacon occurs 3 -0.292 about 103 mes more rapidly than 4 -0.406 butadiene plus ethylene. LUMO coeff. 1 0.615 • The HOMO and LUMO coefficients clearly predict the head to tail regioselecvity to be 2 -0.437 preferred, and it is, by about 75% to 25%.

hp://chemistry.umeche.maine.edu/CHY556/Cyclo3.html Recent Advances in Natural Product Synthesis by Using Intramolecular Diels-Alder Reacons

Ken-ichi Takao, Ryosuke Munakata, and Kin-ichi Tadano

Chem. Rev., 105 (12), 4779 -4807, 2005. J. Org. Chem. 2002, 67, 4501. Org. Le. 1999, 1, 663. J. Org. Chem. 2000, 65, 8595. Reações de Cicloadição [2+2] Cicloadição [4+2]: permitida em condições térmicas Cicloadição [2+2]: proibida por simetria orbitalar em condiçōes termicas Cicloadição [2+2] em condições fotoquimicas

à alcenos eletronicamente idênticos

Cicloadição [2+2] de alcenos eletronicamente diferentes

Paterno-Büchi Reaction

Cicloadição [2+2] de cetenos em condições termicas