Clean Inversion of Configuration in the Pd-Catalyzed Cross-Coupling of 2-Bromo-1,3-dienes
摘要:
The Pd-catalyzed cross-coupling reaction of 2-bromo-1,3-dienes derived from alkyl aldehydes, especially with Cl2Pd(DPEphos) as a catalyst, proceeds with clean stereoinversion of the Br-bearing C=C bond to produce in high yields and in high stereoselectivity (>/=97-98%) conjugated Z,E dienes of potentially high utility in the synthesis of complex natural products. The observed stereoinversion cannot be readily accommodated by the widely accepted pi-sigma-pi rearrangement mechanism for isomerization of ordinary allylpalladium derivatives.
A Practical in situ Generation of the Schwartz Reagent. Reduction of Tertiary Amides to Aldehydes and Hydrozirconation
作者:Yigang Zhao、Victor Snieckus
DOI:10.1021/ol403183a
日期:2014.1.17
A new, highly efficient in situ protocol (Cp2ZrCl2/LiAlH(OBu-t)3) is described for the generation of the Schwartz reagent which provides a convenient method for the amide to aldehyde reduction and the regioselective hydrozirconation–iodination of alkynes and alkenes. Highlighted are chemoselective reductions of benzamides derived by directedorthometalation (DoM) chemistry, allowing the synthesis
描述了一种新的高效原位实验方案(Cp 2 ZrCl 2 / LiAlH(OBu- t)3),用于产生Schwartz试剂,该试剂为酰胺到醛的还原以及炔烃的区域选择性加氢锆化加碘提供了便利的方法。和烯烃。突出显示的是通过定向邻位金属化(D o M)化学反应生成的苯甲酰胺的化学选择性还原,可合成有价值的1,2,3-取代的苯甲醛。单步三组分过程在非常短的反应时间内进行,显示出极好的官能团相容性,并使用廉价且长期保存的稳定还原剂。
Stereospecific Iron-Catalyzed Carbon (sp<sup>2</sup>)–Carbon (sp<sup>2</sup>) Cross-Coupling of Aryllithium with Vinyl Halides
作者:Peng Chen、Zhi-Yong Wang、Xiao-Shui Peng、Henry N.C. Wong
DOI:10.1021/acs.orglett.1c01318
日期:2021.6.4
We present herein an efficient synthetic protocol involving iron-catalyzed cross-coupling of organolithium compounds with vinyl halides as key coupling partners. More than 30 examples were obtained with moderate to good yields and high stereoselectivities. The practicality of this method is evidenced by a gram-scale synthesis. In addition, a preliminary mechanistic investigation was also performed
Schwartz Reagents: Methods of In Situ Generation and Use
申请人:Zhao Yigang
公开号:US20100145060A1
公开(公告)日:2010-06-10
Embodiments of the invention provide a method of using Schwartz Reagent, Cp
2
Zr(H)Cl, without accumulating or isolating it. Methods provide mixtures of Cp
2
ZrCl
2
, reductants that selectively reduce Cp
2
ZrCl
2
, and substrates. After reaction of Cp
2
ZrCl
2
and the reductant, an intermediate reduction product is formed, apparently Schwartz Reagent. The in situ Schwartz Reagent then selectively reduces certain functional groups on the substrate. Substrates include tertiary amides, tertiary benzamides, aryl O-carbamates, and heteroaryl N-carbamates, which are reduced to aldehydes, benzaldehydes, aromatic alcohols, and heteroaromatics, respectively. Compared to prior methods, reagents are inexpensive and stable, reaction times are short, and reaction temperature in certain cases is conveniently room temperature. It has been estimated that using the in situ method described herein instead of synthesized or commercially obtained Schwartz Reagent provides a 50% reduction in cost.
The nickel-catalyzed electroreductive conjugate addition of (Z)- or (E)-alkenyl halides to electron-deficient olefins in the presence of a sacrificial iron rod as the anode proceeds with complete retention of the stereochemistry of the alkenyl part and affords functionalized isomerically pure (Z)- or (E)-olefins in high yield.
A new approach for highly efficient and enantioselective alkenylation of aldehydes promoted by an easily accessible cobalt-based complex was developed. This protocol represents the first example of incorporating a wide range of alkenyl groups with diversified substitution patterns as well as axial stereogenicity into enantioenriched allylic alcohols.