Synthesis of enantioenriched .alpha.-hydroxy-.alpha.-allenylacetic acids by [2,3] Wittig rearrangement of .alpha.-(propargyloxy)acetates
摘要:
Optically active (R)-(propargyloxy)acetic esters 5, available in ca. 90% ee through reduction of alkynones 2 with Chirald-LiAlH4 followed by alkylation with chloroacetic acid and esterification with CH2N2, undergo highly stereoselective [2,3] rearrangement upon treatment with LDA in THF at -78-degrees-C followed by Cp2ZrCl2 to afford alpha-(S)-hydroxy-beta-(R)-allenic esters 7 with complete transfer of chirality and > 90% diastereoselectivity. Upon treatment with TESOTf in Et3N the (R)-(propargyloxy) acetic esters 5 afford the diastereomeric alpha-(R)-hydroxy-beta-(R)-allenic esters 8 stereoselectively. Both hydroxy esters 7 and 8 cyclize stereospecifically to trans- and cis-2,5-dihydrofurans 13-15 and 17-19 upon treatment with AgNO3-CaCO3, PhSeCl, or NBS.
An efficient RhII -catalyzed synthesis of functionalized α-vinyl aldehydes with high E/Z stereoselectivity was developed. The reaction mediates the cyclopropanation of enaminones with vinyl carbenoids that are generated from cyclopropenes in situ to give the aminocyclopropane intermediates. Selective C-C bond cleavage of the cyclopropane intermediates leads to formation of α-vinyl aldehyde derivatives
An Unexpected Domino Reaction of β-Keto Sulfones with Acetylene Ketones Promoted by Base: Facile Synthesis of 3(2<i>H</i>
)-Furanones and Sulfonylbenzenes
作者:Wei Tong、Qian-Yu Li、Yan-Li Xu、Heng-Shan Wang、Yan-Yan Chen、Ying-Ming Pan
DOI:10.1002/adsc.201700830
日期:2017.11.23
An unexpected domino reaction of β‐keto sulfones with acetylene ketones has been developed. The domino reaction of β‐keto sulfones with diynones proceeded smoothly in the presence of 30 mol% K2CO3 without other additives, and afforded the novel 3(2H)‐furanone derivatives. On replacing the diynones with terminal alkyne ketones, the reaction regioselectivity was changed and sulfonylbenzenes were obtained
β-酮砜与乙炔酮发生了意想不到的多米诺反应。在没有其他添加剂的情况下,在30 mol%K 2 CO 3的存在下,β-酮砜与二炔酮的多米诺反应顺利进行,得到了新颖的3(2 H)-呋喃酮衍生物。用末端炔烃酮取代二炔酮后,反应区域选择性改变,并通过苯环化获得磺酰苯,收率很高。
A Silica Gel-Supported Ruthenium Complex of 1,4,7-Trimethyl-1,4,7-triazacyclononane as Recyclable Catalyst for Chemoselective Oxidation of Alcohols and Alkenes by <i>tert</i>-Butyl Hydroperoxide
作者:Wai-Hung Cheung、Wing-Yiu Yu、Wing-Ping Yip、Nian-Yong Zhu、Chi-Ming Che
DOI:10.1021/jo0204404
日期:2002.11.1
The supported Ru catalyst can effect facile oxidation of alcohols by tert-butyl hydroperoxide (TBHP). Primary and secondary benzyl, allylic, and propargylicalcohols were transformed to their corresponding aldehydes and ketones in excellent yields; no oxidation of the C=C and Ctbd1;C bonds was observed for the allylic and propargylicalcoholoxidations. Likewise alkene epoxidation by TBHP can be achieved
Gold(I)-catalyzedhighlyenantioselective intermolecular [4 + 2] cycloaddition is shown with ynones and cyclohexadiene. Various bicyclo[2.2.2]octadiene derivatives are produced in high yields (up to 99%) with good enantioselectivity (up to 96% ee). Key to the success is generation of the gem-digold terminal alkyne as a catalytic on-cycle species. As proof of the gem-digold catalysis, a positive nonlinear
Highly efficient and enantioselective hydrogenation of quinolines and pyridines with Ir-Difluorphos catalyst
作者:Weijun Tang、Yawei Sun、Lijin Xu、Tianli Wang、Qinghua Fan、Kim-Hung Lam、Albert S. C. Chan
DOI:10.1039/c002668a
日期:——
resulted in a highly efficient catalyst system for asymmetrichydrogenation of quinolines at quite low catalyst loadings (0.05–0.002 mol%), affording the corresponding products with high enantioselectivities (up to 96%), excellent catalytic activities (TOF up to 3510 h−1) and productivities (TON up to 43000). The same catalyst was also successfully applied to the asymmetrichydrogenation of trisubstituted