Tandem intramolecular silylformylation and silicon-assisted cross-coupling reactions. synthesis of geometrically defined alpha,beta-unsaturated aldehydes.
The palladium- and copper-catalyzed cross-coupling reactions of cyclic silyl ethers with aryl iodides are reported. Silyl ethers 3 were readily prepared by intramolecular silylformylation of homopropargyl silyl ethers 2 under a carbon monoxide atmosphere. The reaction of cyclic silyl ethers 3with various aryl iodides 7 in the presence of [(allyl)PdCl](2), CuI, a hydrosilane, and KF.2H(2)O in DMF at room temperature provided the alpha,beta-unsaturated aldehyde coupling products 8 in high yields. The need for copper in this process suggested that transmetalation from silicon to copper is an important step in the mechanism. Although siloxane 3 and the product 8 are not stable under basic conditions, KF.2H(2)O provided the appropriate balance of reactivity toward silicon and reduced basicity. The addition of a hydrosilane to [(allyl)PdCl](2) was needed to reduce the palladium(II) to the active palladium(0) form.
Denmark
Scott E
SE
Department of Chemistry, Roger Adams Laboratory, University of Illinois, Urbana, Illinois 61801, USA. denmark@scs.uiuc.edu
Kobayashi
Tetsuya
T
D000447:Aldehydes / Q000138:chemical synthesis*; D000475:Alkenes / Q000737:chemistry; D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D003500:Cyclization; D004988:Ethers, Cyclic / Q000138:chemical synthesis*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry*; D013237:Stereoisomerism
D000447:Aldehydes; D000475:Alkenes; D004988:Ethers, Cyclic; D009942:Organometallic Compounds; D010165:Palladium; D003300:Copper; D012825:Silicon