- Sequential cyclosulfonylation and alkylation as a versatile strategy for dihydropyran synthesis
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Deprotonation of 3,4-dihydro-6-(p-toluenesulfonylmethyl)-2H-pyran (2) with n-BuLi and alkylation of the lithiated allyl sulfone gives good to excellent yields of monoalkylated products 3. No γ-substitution is observed in the monoalkylated products. A seco
- Edwards, Gavin L.,Sinclair, David J.
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- Generation and reaction of carbenes from α-oxacyclo-N-aziridinyl imines - A new method for ring expansion of cyclic ethers
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α-Oxetanyl-N-aziridinyl imines undergo ring expansion on heating to afford dihydrofurans via alkylidenecarbenes, whereas heating α-tetrahydrofuranyl and α-tetrahydropyranyl N-aziridinyl imines affords the ring expanded cyclic enol ethers via alkyl carbene
- Kim, Sunggak,Yoon, Joo-Yong,Cho, Chang Mook
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- An olefin metathesis/double bond isomerization sequence catalyzed by an in situ generated ruthenium hydride species
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The direct conversion of allyl ethers to cyclic enol ethers using an olefin metathesis/double bond migration sequence is described. Ruthenium carbene complexes were activated to catalyze the double bond migration step by addition of hydride sources, such
- Schmidt, Bernd
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- Ruthenium-catalyzed olefin metathesis double-bond isomerization sequence
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A novel ruthenium-catalyzed tandem ring-closing metathesis (RCM) double-bond isomerization reaction is described in this paper. The utility of this method for the efficient syntheses of five-, six-, and seven-membered cyclic enol ethers is demonstrated. It relies on the conversion of a metathesis-active ruthenium carbene species to an isomerization-active ruthenium-hydride species in situ. This conversion is achieved by using various additives. Scope and limitations of the different protocols are discussed, and some mechanistic considerations based on 31P and 1H NMR spectroscopic studies are presented.
- Schmidt, Bernd
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p. 7672 - 7687
(2007/10/03)
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- Carbene reactions of α-oxacyclo- and α-azacyclo-N-aziridinylimines: Effect of heteroatom and ring size in the ring expansion reaction
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Carbenes, generated from thermolysis of α-oxacyclo- and α-azacyclo-N-aziridinylimines in refluxing toluene, underwent ring expansions via insertion of alkyl carbenes into carbon-carbon bonds and intramolecular ammonium ylide formations, respectively. Ring expansion reaction of α-oxetanyl-N-aziridinylimines occurred via alkylidenecarbene intermediates, whereas thermal reaction of α-azetidinyl-N-aziridinylimines afforded α-aminoacetylene compounds via 1,2-H migration of alkylidenecarbene intermediates.
- Kim,Yoon
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p. 1622 - 1630
(2007/10/03)
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- ALKYLATION REACTIONS OF ANIONS DERIVED FROM 2-BENZENESULPHONYL TETRAHYDROPYRAN AND THEIR APPLICATION TO SPIROKETAL SYNTHESIS
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Reaction of 3,4-dihydro-2H-pyran or 2-methoxytetrahydropyran with benzenesulphinic acid gave 2-benzenesulphonyl tetrahydropyran (1).Deprotonation of (1) followed by alkylation with carbonyl compounds or halides gave cyclic enol ether addition products by
- Ley, Steven V.,Lygo, Barry,Sternfeld, Francine,Wonnacott, Anne
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p. 4333 - 4342
(2007/10/02)
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- WITTIG AND HORNER-WITTIG COUPLING REACTIONS OF 2-SUBSTITUTED CYCLIC ETHERS AND THEIR APPLICATION TO SPIROKETAL SYNTHESIS
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Wittig and Horner-Wittig coupling reactions of tetrahydropyran or tetrahydrofuran 2-triphenylphosphonium salts or 2-diphenylphosphine oxides with aldehydes and lactols affords good yields of the corresponding enol ethers.In selected examples these enol ether products may be further converted to spiroketals some of which are natural pheromones derived from Dacus oleae and Paravespula vulgaris.
- Ley, Steven V.,Lygo, Barry,Organ, Helen M.,Wonnacott, Anne
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p. 3825 - 3836
(2007/10/02)
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