Reactions of Nitroalkenes with Nitroalkanes or Sulfur Ylides Catalyzed by Amine-Thiourea Bifunctional Polymeric Organocatalysts
作者:Patrick Toy、Jinni Lu
DOI:10.1055/s-0031-1289900
日期:2011.12
Non-cross-linked and cross-linked bifunctional polystyrenes bearing both amine and thiourea groups have been synthesized and used as organocatalysts in reactions between nitroalkenes and nitroalkanes or sulfur ylides. Control experiments using monofunctional polymers with only either amine or thiourea groups attached indicated that both functional groups were essential for efficient catalysis of the reactions studied. The non-cross-linked polystyrene was soluble in typical organic solvents and was used as a homogeneous catalyst, while the cross-linked polystyrene was used as a heterogeneous catalyst.
Diastereoselective Synthesis
of <i>syn</i>-1,3-Dinitro Compounds by Michael Addition
of Nitroalkanes to Nitroalkenes with a Thiourea Catalyst
作者:William Wulff、Constantinos Rabalakos
DOI:10.1055/s-0028-1083532
日期:——
An operationally simple method has been developed for the conjugate addition of nitroalkanes to b-nitrostyrene with the use of thiourea catalysis. The reaction affords good yields of syn-1,3- dinitro adducts with only 2% catalyst loading.
Enantioselective Organocatalytic Direct Michael Addition of Nitroalkanes to Nitroalkenes Promoted by a Unique Bifunctional DMAP-Thiourea
作者:Constantinos Rabalakos、William D. Wulff
DOI:10.1021/ja805390k
日期:2008.10.15
synthesized, and evaluated for the asymmetric Michael addition of nitroalkanes to nitroalkenes. The obdurate nature of this reaction has made this a formidable challenge to subdue by asymmetric catalysis. The catalyst design includes a thiourea function to activate the nitroalkene by a double H-bond and a 4-dimethylaminopyridine unit to deprotonate the nitroalkane and to bind the resulting nitronate anion also
设计、合成并评估了一种用于硝基烷烃与硝基烯烃的不对称迈克尔加成反应的新催化剂。这种反应的顽固性质使其成为通过不对称催化克服的艰巨挑战。催化剂设计包括硫脲功能,通过双 H 键和 4-二甲氨基吡啶单元激活硝基烯烃,使硝基烷烃去质子化,并通过双 H 键结合所得硝基阴离子。催化剂的手性支架是 2,2'-diamino-1,1'-binaphthalene (BINAM),通过硫脲单元和二甲氨基吡啶部分 (DMAP) 通过两个氨基连接制备双共轭物. 所得催化剂将影响硝基烷烃与各种硝基苯乙烯的反应,并在 10 种底物范围内提供出色的不对称诱导 (91-95% ee)。值得注意的是,不对称诱导随着催化剂负载量的降低而增加,在 2 mol% 的负载下速率和诱导之间的最佳折衷。