lec13_handout - orbitals combine Cycloadditions proceed by...

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13 Massachusetts Institute of Technology Organic Chemistry 5.13 October 8, 2003 Prof. Timothy F. Jamison Notes for Lecture #13 Cycloaddition Reactions – The Diels-Alder Reaction Molecule of the Day cantharidin Cantharidin irritant Cantharis vesicatoria found in the eponymous, alleged aphrodisiac. Several chemistry and in many of these a Diels-Alder reaction was a key step. O Me Me O O O is a powerful isolated from , a.k.a. the "blistering beetle" or "Spanish fly", and is research groups have prepared cantharidin by total synthesis, Cycloaddition: A pericyclic reaction in which 2 separate conjugated, overlapping arrays of
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Unformatted text preview: orbitals combine . Cycloadditions proceed by way of a cyclic transition state , and 2 sigma bonds are formed during the course of the reaction. A suprafacial process ("s" in the table below) is one in which the bonds made or broken lie on the same face of the orbital array undergoing reaction. In an antarafacial process ("a"), the newly formed or broken bonds lie on opposite faces of the reacting orbital array. Woodward-Hoffmann Rules for Cycloadditions Stereochemical Course # Electrons Thermal Mode Photochemical Mode 4n + 2 [s + s] [s + a] 4n [s + a] [s + s]...
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This note was uploaded on 11/27/2011 for the course CHEMICAL E 20.410j taught by Professor Rogerd.kamm during the Spring '03 term at MIT.

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