Reactions of Trimethylsilyl Dienol Ethers with Palladium(II) Salts: Formation of Formyl-Substituted η<sup>3</sup>-Allylpalladium Complexes and 4-Acyloxy-2-Alkenals
作者:Björn C. Söderberg、Angela K. Berry、Paula C. Jones
DOI:10.1021/om971048x
日期:1998.3.1
to excellent yield. In contrast, using palladium diacetate as the palladium(II) source produces 4-acetyloxy-substituted 2-alkenals. Excellent stereoselection in favor of the E-alkenal is usually observed. The corresponding benzoic acid esters can be prepared, with similar stereoselection, using 1-(trimethylsilyloxy)-1,3-dienes and palladium diacetate in the presence of an excess sodium benzoate.
作者:Primke, Hartmut、Sarin, Gurdeep S.、Kohlstruk, Stephan、Adiwidjaja, Gunadi、Meijere, Armin de
DOI:——
日期:——
Reactions of co-ordinated ligands. Part 50. The synthesis of functionalised η<sup>3</sup>-allyl complexes of molybdenum and their conversion into η<sup>4</sup>-s-trans-1,3-dienes
作者:Stephen A. Benyunes、Alessandra Binelli、Michael Green、Michael J. Grimshire
DOI:10.1039/dt9910000895
日期:——
Reaction of the labile bis(acetonitrile) complexes [Mo(NCMe)2(CO)2(eta-5-L)][BF4] (L = C9H7 1 or C5Me5 2) with the 1-trimethylsilyloxybuta-1,3-dienes Me3SiOCH = CR1CH = CHR2 (R1 = R2 = H; R1 = Me, R2 = H; R1 = H, R2 = Me) results in initial co-ordination of the diene followed by a rapid desilylation affording the 4-oxo-functionalised allyls [Mo(eta-3-CR2R3CHCR1CHO)(CO)2(eta-5-L)] 4 and 6-9. Complexes 4 and 6-9 are generated in the form of isomeric mixtures, arising through syn-anti isomerism at C2 of the allyl ligand together with the presence of non-interconvertible exo and endo orientations for the latter with respect to the metal fragment. Addition of Ph3P = CH2 to 6 (R1 = R2 = R3 = H) and 7 (R1 = Me, R2 = R3 = H) effects smooth conversion into the eta-3-pentadienyl complexes [Mo(eta-3-CR2R3CHCR1CHCH2)(CO)2(eta-5-C5Me5)] 11 (R1 = R2 = R3 = H) and 12 (R1 = Me, R2 = R3 = H). The low-temperature (-78-degrees-C) protonation of compounds syn-6-8 using CF3SO3H results in a quantitative transformation into the s-trans-diene cations [Mo(eta-4-s-trans-trans-HOCHCR1CHCR2R3)-(CO)2(eta-5-C5Me5)][CF3SO3] 13 (R1 = R2 = R3 = H), 14 (R1 = Me, R2 = R3 H) and 15 (R1 = R3 = H, R2 = Me), characterised in situ by H-1 NMR spectroscopy. Above -30-degrees-C, 13-15 undergo an irreversible rearrangement in solution to the corresponding s-cis diene cations. Deprotonation of 13-15 by treatment with NEt3 regenerates the syn isomers of 6-8, whilst the s-cis diene cations produce only the anti species under the same conditions. These results are interpreted in terms of an overall retention of stereochemistry of the C4 ligand throughout these manipulations. The eta-3-pentadienyl complexes 11 and 12 undergo analogous transformations upon addition of CF3SO3H producing the thermally unstable s-trans-diene cations [Mo(eta-4-s-trans-trans-MeCHCRCHCH2)(CO)2(eta-5-C5Me5)][CF3SO3] 16 (R = H) and 17 (R = Me), which are likewise converted into their s-cis isomers at temperatures in excess of -20-degrees-C.
γ-selectivity in the ceric ammonium nitrate promoted oxidative addition of silyl dienol ethers to silyl enol ethers
作者:Anna Belli Paolobelli、David Latini、Renzo Ruzziconi
DOI:10.1016/s0040-4039(00)61663-5
日期:1993.1
Trimethylsilyl dienol ethers are easily oxidized by cericammoniumnitrate to give α-carbonylallyl radicals which are able to add to enolic carbon-carbon double bonds with very high γ regioselectivity, allowing the method to be applied to the synthesis of 6-oxo-α,β-unsaturated carbonyl compounds.