Late Transition Metal Catalysis: examples of oxidative addition and reductive elimination used in industry 1. Alkene Hydrogenation many proceed by ox. addn / red. elim (see below) but radical - + and heterolytic H2 transfer (H and H sequentially) also known Wilkinson’s catalyst (next page) . selective for C=C over C=O and CN . does not scramble H and D . exclusively syn H2 addition (see eg. below) . commercially available 2. Hydroformylation (Oxo process) O R + H2 + CO R H synthesis gas 3. Monsanto Acetic Acid Process (carbonylation of MeOH) main use of acetic acid is in the synthesis of vinyl acetate, cellulose acetate, pharmaceuticals, dyes and pesticides. Acetic acid for food purposes is made by biocatalysis. the Monsanto process dominates the market but older methods such as Wacker chemistry (oxidation of ethylene via acetaldehyde – see section 5) are still practiced. conditions: 180 C / 30-40 atm / 10-3 M catalyst 4. Pd catalyzed cross couplings (2010 Nobel Prize) general mechanism is the same for many of the variants; they simply differ in the transmetallation reagent General mechanism: Pd2+ or Pd0 precatalyst concerted (sp2) or stepwise (sp3) R'X OA PdL2(solv) - solvent R'-R L R' Pd L X RE Isomerize L R' solvent Pd X L E-R L R' L R' Pd Pd L R R L Transmetallation Isomerize E-X Meet the family… Reaction E R’ type R type Promoter ! n 2 Stille SnBu 3 wide range sp>sp >aryl CuI, LiCl 3 >allylic>sp 2 2 - Hiyama SiR”3 sp , aryl sp , aryl F (required) $ 2 2 Suzuki B(OH)2 sp , aryl sp , aryl, base alkyl alkyl NaOH or Cs2CO3 Kumada MgX various various Negishi $ ZnX various various Sonogashira* Cu sp2>aryl CCR CuI, base e- poor>e- rich e- rich>e- poor (* without Pd this is the Stephens-Castro) $ awarded 2010 Nobel Prize in Chemistry (along with Heck) ! deceased 1989 in UA 232 crash in Sioux City, Iowa (http://www.youtube.com/watch?v=OAiYkX-Woh0) .