1,721,260 research outputs found
Regio- and diastereoselective cyclization reactions of free and masked 1,3-dicarbonyl dianions with 1,2-dielectrophiles
No full textDespite their simplicity and synthetic usefulness, cyclisation reactions of 1,3-dicarbonyl dianions with 1,2-dielectrophiles are problematic, since both dianions and 1,2-dielectrophiles are highly reactive compounds (low reactivity matching). In addition, 1,2-dielectrophiles are often rather labile, and reactions with nucleophiles can result in polymerisation, decomposition, formation of open-chained products, elimination or SET-reactions. These intrinsic limitations can be overcome by a proper reactivity tuning and by the use of electroneutral dianion equivalents (masked dianions) in Lewis acid catalysed reactions. The cyclisations reported herein allow for an efficient, regio- and stereoselective one-pot synthesis of biologically relevant ring systems
Cyclization reactions of 1,3-bis-silyl enol ethers and related masked dianions
No full textDespite their simplicity and synthetic usefulness, reactions of 1.3-dicarbonyl dianions are often problematic, since they represent highly reactive compounds (low reactivity matching). In addition, functionalized electrophiles are often rather labile and reactions with strong nucleophiles can result in polymerisation, decomposition, formation of open-chain products, elimination, or SET-reactions. These intrinsic limitations can be overcome by the use of 1,3-bis-silyl enol ethers, electroneutral 1,3-dicarbonyl dianion equivalents, in Lewis acid catalyzed reactions. 1 Synthesis and Rearrangements of 1,3-Bis-Silyl Enol Ethers 2 Aldehydes and Ketones 3 Acetals 4 1,2-Dicarbonyl Derivatives 5 1,3-Dicarbonyl Derivatives 6 Orthoesters 7 1,4-Dicarbonyl Derivatives 8 Carboxylic Acid Derivatives 9 Oxalyl Chloride 10 Epoxides 11 Michael Reactions 12 [4+2] Cycloadditions 13 SET Reaction
Cyclization reactions of 1,3-bis-silyl enol ethers and related masked dianions
No full textDespite their simplicity and synthetic usefulness, reactions of 1.3-dicarbonyl dianions are often problematic, since they represent highly reactive compounds (low reactivity matching). In addition, functionalized electrophiles are often rather labile and reactions with strong nucleophiles can result in polymerisation, decomposition, formation of open-chain products, elimination, or SET-reactions. These intrinsic limitations can be overcome by the use of 1,3-bis-silyl enol ethers, electroneutral 1,3-dicarbonyl dianion equivalents, in Lewis acid catalyzed reactions. 1 Synthesis and Rearrangements of 1,3-Bis-Silyl Enol Ethers 2 Aldehydes and Ketones 3 Acetals 4 1,2-Dicarbonyl Derivatives 5 1,3-Dicarbonyl Derivatives 6 Orthoesters 7 1,4-Dicarbonyl Derivatives 8 Carboxylic Acid Derivatives 9 Oxalyl Chloride 10 Epoxides 11 Michael Reactions 12 [4+2] Cycloadditions 13 SET Reaction
New strategies for the development of an asymmetric version of the Baylis-Hillman reaction
No full textTetra-n-propyl ammonium perruthenate (TPAP) - An efficient and selective reagent for oxidation reactions in solution and on the solid phase
No full textRegioselective synthesis and acylation of cyclic bis-(trimethylsiloxy)-1,3-dienes - New and versatile 1,3-dianion synthons
No full textCyclohexanone-derived bis-(trimethylsiloxy)-1,3-dienes were regioselectively prepared by the use of different silylating systems. These dienes represent new and versatile 1,3-dianion synthons in Lewis-acid catalyzed acylation reactions
Efficient synthesis of functionalized 4,5-benzotropones by regioselective cyclization of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with phthalic dialdehyde
No full textThe reaction of 1,3-bis(trimethylsiloxy)-1,3-butadienes with phthalic dialdehyde resulted in regioselective formation of functionalized 4,5-benzotropones
New and regioselective synthesis of 4-ylidene-tetronic acids by Lewis-acid catalyzed cyclization of 4-alkoxy-bis-(trimethylsiloxy)-1,3-diene with oxalyl chloride
No full textA new approach for the synthesis of 4-ylidene-tetronic acids is reported which involves Me3SiOTf-catalyzed, regio- and stereoselective cyclization of 4-alkoxy-bis-(trimethylsiloxy)-1,3-dienes with oxalyl chloride and subsequent chemoselective deprotection of the 3-hydroxy-group
Regio- and diastereoselective synthesis of lissoclinolide analogues by Lewis acid catalyzed cyclization of the first 1,5-bis(trimethylsilyloxy)-1,3,5-hexatrienes with oxalyl chloride
No full textThe Lewis acid catalyzed cyclization of 1,5-bis(trimethylsilyloxy)-1,3,5-hexatrienes with oxalyl chloride resulted in formation of polyunsaturated butenolides
Regio- and diastereoselective synthesis of functionalized cyclopentenones by domino Michael-Ester-Wittig reactions of (3-alkoxycarbonyl-2-oxopropylidene)triphenylphosphoranes with maleic diesters
No full textThe domino Michael-Ester-Wittig reaction of maleic diesters with (3-alkoxycarbonyl-2-oxopropylidene)triphenylphosphoranes resulted in regio- and diastereoselective formation of functionalized cyclopentenones
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