An operationally simple protocol was designed for the enantioselective silane reduction (ESR) of ketones using air- and moisture-stable [Ir(OMe)(cod)]<sub>2</sub> (cod = 1,5-cyclooctadiene) (3) as a metal ...An operationally simple protocol was designed for the enantioselective silane reduction (ESR) of ketones using air- and moisture-stable [Ir(OMe)(cod)]<sub>2</sub> (cod = 1,5-cyclooctadiene) (3) as a metal catalyst precursor. This reaction was driven by chiral hydroxyamide-functionalized azolium salt 2. The catalytic ESR reaction could be performed under benchtop conditions at room temperature. Treatment of 2 with 3 in THF yielded the monodentate IrCl(NHC)(cod) (NHC = N-heterocyclic carbene) complex 4 in 93% yield, herein the anionic methoxy ligand of 3 serves as an internal base that deprotonates the azolium ring of 2. The well-defined Ir complex 4 catalyzed the ESR reaction of propiophenone (6) with (EtO)<sub>2</sub>MeSiH using the pre-mixing reaction procedure. Based on this success, the catalytic ESR reaction was designed and implemented using an in situ-generated NHC/Ir catalyst derived from 2 and 3. Thus, a wide variety of aryl ketones could be reduced to the corresponding optically active alcohols in moderate to excellent stereoselectivities at room temperature without temperature control. Since the high catalytic activity of 3 was observed, we next evaluated several other transition metal catalyst precursors for the catalytic ESR reaction under the influence of 2. This evaluation revealed that Ir(acac)(cod) (acac = acetylacetonate) (28) and [IrCl(cod)]<sub>2</sub> (5) can be successfully used as metal catalyst precursors in the ESR reaction.展开更多
Comprehensive Summary,The asymmetric partial reduction of 1,3-diketones stands as a straightforward pathway to access optically active β-hydroxyketones. In this paper, an asymmetric Piers-type hydrosilylation of 2,2-...Comprehensive Summary,The asymmetric partial reduction of 1,3-diketones stands as a straightforward pathway to access optically active β-hydroxyketones. In this paper, an asymmetric Piers-type hydrosilylation of 2,2-difluoro-1,3-diketones was successfully realized by using a frustrated Lewis pair of chiral borane and tricyclohexylphosphine as a catalyst, delivering a variety of α,α-difluoro-β-hydroxyketones in high yields with up to 99% ee. Significantly, no over-reduced diol products were observed even with an excess amount of silanes. The product can be conveniently converted to α,α-difluoro-β-hydroxyester or 1,3-anti-diol via an oxidation with m-CPBA or a reduction with DIBAL-H without obvious loss of ee.展开更多
受阻路易斯酸碱对(frustrated Lewis pairs,FLPs)是目前合成化学的前沿挑战性研究领域之一,为非金属催化的氢化和Piers-type硅氢化反应提供了非常有效的途径.近年来,相关研究取得了重要的研究进展,但是相应的不对称反应发展比较缓慢.缺...受阻路易斯酸碱对(frustrated Lewis pairs,FLPs)是目前合成化学的前沿挑战性研究领域之一,为非金属催化的氢化和Piers-type硅氢化反应提供了非常有效的途径.近年来,相关研究取得了重要的研究进展,但是相应的不对称反应发展比较缓慢.缺乏高效、高选择性的手性催化剂仍然是制约这一领域快速发展的重要因素.手性螺环是配体设计中的优势骨架.基于前期所发展的联萘骨架手性FLP催化剂及其在不对称催化氢化和硅氢化反应的应用,设计并合成了基于手性螺环骨架的手性双烯,通过与HB(C6F5)2的硼氢化反应原位制备了新型手性硼烷路易斯酸.利用其与三叔丁基膦形成的手性受阻路易斯酸碱对催化剂,成功地实现了简单酮的不对称Piers-type硅氢化反应,反应的对映选择性最高可达90%.展开更多
A chiral Lewis base organocatalyzed enantioselective hydrosilylation ofa-keto ketimines was investigated.The reactions afforded various enantioenriched a-amino ketones with good yields（up to 95％） in moderate to goo...A chiral Lewis base organocatalyzed enantioselective hydrosilylation ofa-keto ketimines was investigated.The reactions afforded various enantioenriched a-amino ketones with good yields（up to 95％） in moderate to good enantioselectivities（up to 98％ e.e.）.Furthermore,one of the products was reduced to a chiral 1,2-amino alcohol.Following cyclization of it with triphosgene generated a cannabinoid receptor 1 （CB 1） inhibitor with good diastereoselectivity.展开更多
A new set of reaction conditions has been established and allowed for the first non-noble Cu（II）-catalyzed asymmetric 1,4-hydrosilylation ofN-aryl β-enamino esters under air to afford a selection ofN-aryl β-amino ...A new set of reaction conditions has been established and allowed for the first non-noble Cu（II）-catalyzed asymmetric 1,4-hydrosilylation ofN-aryl β-enamino esters under air to afford a selection ofN-aryl β-amino acid es- ters of moderate-to-good enantiopurities （ee up to 91%）.展开更多
Hydrosilylation is one of the most important reactions in synthetic chemistry and ranks as a fundamental method to access organosilicon compounds in industrial and academic processes.However,the enantioselective const...Hydrosilylation is one of the most important reactions in synthetic chemistry and ranks as a fundamental method to access organosilicon compounds in industrial and academic processes.However,the enantioselective construction of chiral-at-silicon compounds via catalytic asymmetric hydrosilylation remained limited and difficult.Here we report a highly enantioselective hydrosilylation of ynones,a type of carbonyl-activated alkynes,using a palladium catalyst with a chiral binaphthyl phosphoramidite ligand.The stereospecific hydrosilylation of ynones affords a series of silicon-stereogenic silylenones with up to 94%yield,>20:1 regioselectivity and 98:2 enantioselectivity.The density functional theory(DFT)calculations were conducted to elucidate the reaction mechanism and origin of high degree of stereoselectivity,in which the powerful potential of aromatic interaction in this reaction is highlighted by the multiple C–H-πinteraction and aromatic cavity-oriented enantioselectivitydetermining step during desymmetric functionalization of Si–H bond.展开更多
文摘An operationally simple protocol was designed for the enantioselective silane reduction (ESR) of ketones using air- and moisture-stable [Ir(OMe)(cod)]<sub>2</sub> (cod = 1,5-cyclooctadiene) (3) as a metal catalyst precursor. This reaction was driven by chiral hydroxyamide-functionalized azolium salt 2. The catalytic ESR reaction could be performed under benchtop conditions at room temperature. Treatment of 2 with 3 in THF yielded the monodentate IrCl(NHC)(cod) (NHC = N-heterocyclic carbene) complex 4 in 93% yield, herein the anionic methoxy ligand of 3 serves as an internal base that deprotonates the azolium ring of 2. The well-defined Ir complex 4 catalyzed the ESR reaction of propiophenone (6) with (EtO)<sub>2</sub>MeSiH using the pre-mixing reaction procedure. Based on this success, the catalytic ESR reaction was designed and implemented using an in situ-generated NHC/Ir catalyst derived from 2 and 3. Thus, a wide variety of aryl ketones could be reduced to the corresponding optically active alcohols in moderate to excellent stereoselectivities at room temperature without temperature control. Since the high catalytic activity of 3 was observed, we next evaluated several other transition metal catalyst precursors for the catalytic ESR reaction under the influence of 2. This evaluation revealed that Ir(acac)(cod) (acac = acetylacetonate) (28) and [IrCl(cod)]<sub>2</sub> (5) can be successfully used as metal catalyst precursors in the ESR reaction.
基金the financial support from the National Natural Science Foundation of China(21825108 and 22331011).
文摘Comprehensive Summary,The asymmetric partial reduction of 1,3-diketones stands as a straightforward pathway to access optically active β-hydroxyketones. In this paper, an asymmetric Piers-type hydrosilylation of 2,2-difluoro-1,3-diketones was successfully realized by using a frustrated Lewis pair of chiral borane and tricyclohexylphosphine as a catalyst, delivering a variety of α,α-difluoro-β-hydroxyketones in high yields with up to 99% ee. Significantly, no over-reduced diol products were observed even with an excess amount of silanes. The product can be conveniently converted to α,α-difluoro-β-hydroxyester or 1,3-anti-diol via an oxidation with m-CPBA or a reduction with DIBAL-H without obvious loss of ee.
基金Project supported by the National Natural Science Foundation of China(No.21825108)~~
文摘受阻路易斯酸碱对(frustrated Lewis pairs,FLPs)是目前合成化学的前沿挑战性研究领域之一,为非金属催化的氢化和Piers-type硅氢化反应提供了非常有效的途径.近年来,相关研究取得了重要的研究进展,但是相应的不对称反应发展比较缓慢.缺乏高效、高选择性的手性催化剂仍然是制约这一领域快速发展的重要因素.手性螺环是配体设计中的优势骨架.基于前期所发展的联萘骨架手性FLP催化剂及其在不对称催化氢化和硅氢化反应的应用,设计并合成了基于手性螺环骨架的手性双烯,通过与HB(C6F5)2的硼氢化反应原位制备了新型手性硼烷路易斯酸.利用其与三叔丁基膦形成的手性受阻路易斯酸碱对催化剂,成功地实现了简单酮的不对称Piers-type硅氢化反应,反应的对映选择性最高可达90%.
基金Supported by the National Natural Science Foundation of China（No.20972155）.
文摘A chiral Lewis base organocatalyzed enantioselective hydrosilylation ofa-keto ketimines was investigated.The reactions afforded various enantioenriched a-amino ketones with good yields（up to 95％） in moderate to good enantioselectivities（up to 98％ e.e.）.Furthermore,one of the products was reduced to a chiral 1,2-amino alcohol.Following cyclization of it with triphosgene generated a cannabinoid receptor 1 （CB 1） inhibitor with good diastereoselectivity.
文摘A new set of reaction conditions has been established and allowed for the first non-noble Cu（II）-catalyzed asymmetric 1,4-hydrosilylation ofN-aryl β-enamino esters under air to afford a selection ofN-aryl β-amino acid es- ters of moderate-to-good enantiopurities （ee up to 91%）.
基金This work was supported by the National Natural Science Foundation of China(21773051,22072035,21703051,21801056,21901056)Zhejiang Provincial Natural Science Foundation of China(LZ18B020001,LY18B020013,LQ19B040001).
文摘Hydrosilylation is one of the most important reactions in synthetic chemistry and ranks as a fundamental method to access organosilicon compounds in industrial and academic processes.However,the enantioselective construction of chiral-at-silicon compounds via catalytic asymmetric hydrosilylation remained limited and difficult.Here we report a highly enantioselective hydrosilylation of ynones,a type of carbonyl-activated alkynes,using a palladium catalyst with a chiral binaphthyl phosphoramidite ligand.The stereospecific hydrosilylation of ynones affords a series of silicon-stereogenic silylenones with up to 94%yield,>20:1 regioselectivity and 98:2 enantioselectivity.The density functional theory(DFT)calculations were conducted to elucidate the reaction mechanism and origin of high degree of stereoselectivity,in which the powerful potential of aromatic interaction in this reaction is highlighted by the multiple C–H-πinteraction and aromatic cavity-oriented enantioselectivitydetermining step during desymmetric functionalization of Si–H bond.
