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456 Organic Chemistry Solutions Manual Now, the Wacker oxidation (p. 1337), by whatever detailed mechanism you prefer, must involv N the addition of water to a Pd(II) π-complex of the alkene and of palladium to give can Pd(0), which is recycled by oxidation with oxygen mediated by copper. CI read R R R R CHO Pd(II) CHO CHO CHO This general aromatic annelation Finally, the pyridine synthesis is simply a double enamine/imine formation between sequence came from Hawaii and the two carbonyl groups. Probably the aldehyde reacts first. (M. A. Tius, Tetrahedron Lett., 1982, 23, 2819). 0 H OH R R R R 0 N N T - CHO imine NH formation Problem 8 Give a mechanism for this carbonylation reaction. Comment on the stereochemistry and explain why the yield is higher if the reaction is carried out under a carbon monoxide atmosphere. N an Ph₃P CI 0 Pd Bu₃Sn Ph₃P CH₂Ph Ph PhCOCI Hence explain this synthesis of part of the antifungal compound COCI 0 I OSiPh₂t-Bu CO₂CH₂Ph CO₂CH₂Ph Bu₃Sn CO₂CH₂Ph AIBN Ph₃P CI Pd OSIPh₂t-Bu Ph₃P CH₂Ph Purpose of the problem Revision of Chapter 47 with practice at Stille coupling and carbonylation. Suggested solution Pu The tin-palladium exchange (transmetallation) occurs (pp. 1326-7) with retention of configuration at the double bond. The exchange of the benzyl group for the benzoyl group is necessary just to get the reaction started. Ph Ph₃P CI Ph₃P The Pd Pd CI Ph₃P CH₂Ph Ph₃P gro Ph Ph 0 Pd PhCOCI Pd + Ph₃P Ph₃P