Enantioselective Construction of Tetrasubstituted Stereogenic Carbons through Brønsted Base Catalyzed Michael Reactions: α′-Hydroxy Enones as Key Enoate Equivalent
作者:Eider Badiola、Béla Fiser、Enrique Gómez-Bengoa、Antonia Mielgo、Iurre Olaizola、Iñaki Urruzuno、Jesús M. García、José M. Odriozola、Jesús Razkin、Mikel Oiarbide、Claudio Palomo
DOI:10.1021/ja510603w
日期:2014.12.24
tetrasubstituted carbon stereocenters in high diastereo- and enantioselectivity in the presence of standard BB catalysts. Experiments show that the α'-oxy ketone moiety plays a key role in the above realizations, as parallel reactions under identical conditions but using the parent α,β-unsaturated ketones or esters instead proceed sluggish and/or with poor stereoselectivity. A series of trivial chemical
催化和不对称迈克尔反应构成了合成中构建新 CC 键的非常强大的工具,但大多数声称具有高选择性的报告仅限于亲核/亲电化合物类型的某些特定组合,只有少数成功的方法处理了全碳四元立体中心。基于手性双功能 Brønsted 碱 (BB) 催化和使用 α'-氧烯酮作为使迈克尔受体具有矛盾的 H 键受体/供体特征,这是一种尚未报道的双齿烯酸设计元素,为解决这一差距做出了贡献。等价物。发现之前证明具有挑战性的一系列烯醇化羰基化合物(即 α-取代的 2-羟吲哚、氰基酯、恶唑酮、噻唑酮、和 azlactones) 到 α'-氧烯酮可以在标准 BB 催化剂存在下以高非对映选择性和对映选择性提供相应的四取代碳立体中心。实验表明,α'-氧基酮部分在上述实现中起着关键作用,因为在相同条件下进行平行反应,但使用母体 α,β-不饱和酮或酯进行缓慢和/或立体选择性差。对加合物中的酮醇部分进行一系列简单的化学操作可以在非常
STEREOSELECTIVE SYNTHESIS OF<i>CIS</i>-α,β-EPOXYESTERS AND ALDEHYDES VIA DIVALENT TIN ENOLATE. A SYNTHESIS OF 2-AMINO-2-DEOXY-D-ARABINITOL
A convenient method for the stereoselective synthesis of cis-α,β-epoxyesters and aldehydes is established according to the Sn(OTf)2 mediated cross aldol reaction between α-bromo-α′-silyloxyketone and aldehyde. The reaction is applied to the stereoselective synthesis of 2-amino-2-deoxy-d-arabinitol.
Enantioselective Conjugate Radical Addition to α‘-Hydroxy Enones
作者:Sunggi Lee、Chae Jo Lim、Sunggak Kim、Rajesh Subramaniam、Jake Zimmerman、Mukund P. Sibi
DOI:10.1021/ol061634z
日期:2006.9
Enantioselectiveconjugate radical addition to alpha'-hydroxy alpha,beta-unsaturated ketones, compounds containing bidentate donors, has been investigated. It has been found that radical additions to alpha'-hydroxy alpha,beta-unsaturated ketones in the presence of Mg(NTf2)2 and bisoxazoline ligand 5a proceeded cleanly, yielding the addition products in high chemical yields and good enantiomeric excesses
Enantioselective Conjugate Addition of <i>N</i>,<i>N</i>-Dialkylhydrazones to α-Hydroxy Enones
作者:David Monge、Eloísa Martín-Zamora、Juan Vázquez、Manuel Alcarazo、Eleuterio Álvarez、Rosario Fernández、José M. Lassaletta
DOI:10.1021/ol071055+
日期:2007.7.1
The activation of alpha-hydroxy enones by the Zn(OTf)2/tBuBOX catalyst enables the enantioselectiveconjugateaddition of 1-methyleneaminopyrrolidine as a neutral d1 synthon. Experimental evidence supports a stereochemical model where a triflate ligand controls the geometry of the catalyst-substrate complex by means of a OH-OTf hydrogen bond. The synthesis of beta-cyano acids illustrates the potential
Catalytic Enantioselective Conjugate Addition of Nitromethane to α′-Hydroxy Enones as Surrogates of α,β-Unsaturated Carboxylic Acids and Aldehydes
作者:Claudio Palomo、Raquel Pazos、Mikel Oiarbide、Jesús M. García
DOI:10.1002/adsc.200606076
日期:2006.7
No base is required for the Mg(II)-catalyzed conjugate addition of nitromethane to α′-hydroxy enones in the presence of molecular sieves. Good enantioselectivities are attained using 3 or 4 Å MS and about 10 mol % of Mg(OTf)2-chiral bisoxazoline complexes. Elaboration of the adducts through oxidative cleavage of the ketol moiety provides an entry to enantioenriched γ-nitro carboxylic acids, while a