Evans. Breit Cheletropic Processes-1 Chem 206 CHELETROPIC REACTIONS: [n+1] Cycloadditions(or Cycloreversions 2+1 CheletropicReaction: Olefins Singlet Carbene Concerted processes in which 2 a-bonds are made(or broken)which terminate at a single atom R Linear Approach: 2 HOMO-LUMO Interactions General HOMO LUMO LUMO HOMO Y Reversion Nonlinear Approach: 2 HOMO-LUMO Interactions Addition 8 LUMO Addition (and Rev and Addition HOMO LUMO HOMO Frontier Orbitals p(empty) Carry out the analysis of the indicated hypotheti Question: what is orientation of carbene relative to attacking olefin?? try of carbeneX Y Z C R R C R R C Y Z C Me Me Y Z Me Me HOMO HOMO SO2 C C C O C C X Y Z C N N N N O R R R R X Y Z X Y Z HOMO HOMO R R C C C C R R S O O S O O C R R Cheletropic Processes-1 Chem 206 2 + 1 CheletropicReaction: Olefins + Singlet Carbene CHELETROPIC REACTIONS: [n+1] Cycloadditions (or Cycloreversions) Concerted processes in which 2 s-bonds are made (or broken) which terminate at a single atom. + [4+2] + [4+1] General p-system Reversion Addition p-system + Singlet-Carbene Addition (and Reversion) Cycloreversion only Reversion and Addition Frontier Orbitals E w 2 w 0 p (empty) sp2 (filled) 0 2 Linear Approach: 2 HOMO-LUMO Interactions LUMO LUMO Nonlinear Approach: 2 HOMO-LUMO Interactions LUMO Carry out the analysis of the indicated hypothetical transformation Evans, Breit predict approach geometry of carbene LUMO Question: what is orientation of carbene relative to attacking olefin??