Tributyltin hydride-mediated radical cyclisation of aldehydes and unsaturated ketones: the synthesis of hydroxy tetrahydrofurans, chromanols and related compounds
作者:David Bebbington、Jon Bentley、Paul A Nilsson、Andrew F Parsons
DOI:10.1016/s0040-4039(00)01586-0
日期:2000.11
The tributyltin hydride-mediated cyclisation of unsaturated ethers bearing an aldehyde or α,β-unsaturated ketone group is reported. Cyclisation proceeds viaaddition of the tributyltin radical to the carbonyl double bond and the resultant O-stannyl ketyl can add intramolecularly to electron-rich double bonds to form hydroxy tetrahydrofurans, chromanols or related compounds.
Tributyltin hydride-mediated radical cyclisation of carbonyls to form functionalised oxygen and nitrogen heterocycles
作者:Jon Bentley、Paul A. Nilsson、Andrew F. Parsons
DOI:10.1039/b202077g
日期:2002.6.7
The tributyltin hydride-mediated cyclisation of unsaturated ethers and aminesbearing an aldehyde or α,β-unsaturated ketone group is reported. Cyclisation proceeds via reversible addition of the tributyltin radical to the carbonyl double bond to form an intermediate O-stannyl ketyl. This nucleophilic radical can add intramolecularly to electron-rich double bonds to form substituted 5- or 6-membered
Asymmetric [2,3]-sigmatropic wittig rearrangement of chiral α-allyloxy-hydrazones
作者:Dieter Enders、Dirk Backhaus、Jan Runsink
DOI:10.1016/0040-4020(95)00982-5
日期:1996.1
[2,3]-Wittig rearrangement of chiral α-allyloxy-hydrazones (S)-3 and (S)-7 proceeds with very good yields (72 – 100%) together with high syn-selectivities (87 – 97%) and asymmetric inductions (63 – 92%) to give the corresponding α-hydroxyhydrazones 4 and 8. Depending on the substitution patterns of the starting material, opticallyactive aliphatic and aromatic α-hydroxyketones 5 or protected cyanohydrins
Intramolecular cycloaddition of novel 1,3-dipoles, N-boranonitrones, was examined. Treatment of O-tert-butyldimethylsilyloximes 9-12 having olefin moieties with 2 equiv of BF3 center dot OEt2 generated N-boranonitrones, which underwent intramolecular cycloaddition to afford N-nonsubstituted cycloadducts 16 (and/or 18) after extractive workup. Despite the Lewis-acidic conditions, the olefin geometry of the substrates was retained in the cycloadducts in the present cycloaddition. The electronic nature of the N-boranonitrones appeared to be electrophilic. In the case of substrate 11c, having an electron-donating methyl group at an internal position of the olefin moiety, the cycloaddition gave the bridged cycloadduct 18b. The cycloaddition proceeded at relatively low temperature, and the diastereoselectivity was high.