The four isomeric 5, 10-pentadecadienals 1, 2, 3 and 4 were prepared by stereo-selective routes from acetylenic precursors. Two of them, 2 and 4, were also made by Wittig reaction from 2-hydroxytetrahydropyran (29). 2-Hydroxytetrahydropyran (29) yields (Z)-5-alkenols efficiently by Wittig reaction, and (Z)-4-hexenol was similarly made from 2-hydroxytetrahydrofuran (66).
Chiral Brønsted Acid Catalyzed Dynamic Kinetic Asymmetric Hydroamination of Racemic Allenes and Asymmetric Hydroamination of Dienes
作者:Jin‐Shun Lin、Tao‐Tao Li、Guan‐Yuan Jiao、Qiang‐Shuai Gu、Jiang‐Tao Cheng、Ling Lv、Xin‐Yuan Liu
DOI:10.1002/anie.201900955
日期:2019.5.20
The first highly efficient and practical chiral Brønsted acid catalyzed dynamic kinetic asymmetric hydroamination (DyKAH) of racemic allenes and asymmetric hydroamination of unactivated dienes with both high E/Z selectivity and enantioselectivity are described herein. The transformation proceeds through a new catalytic asymmetric model involving a highly reactive π‐allylic carbocationic intermediate
The photoamination of 1-arylalka-1,3-dienes 1a–f and
1-aryl-4-phenylbuta-1,3-dienes 1g–k with NH3 in the
presence of p-dicyanobenzene (DCB) gives 4-amino-1-arylalk-2-enes
2a–f and 1-amino-1,4-diarylbut-2-enes 2g–k, respectively. The
photoamination proceeds by nucleophilic addition of NH3 to the
cation radicals of 1+˙ generated by photoinduced
electron transfer to DCB. The regiochemistry of 2 is related to the
distribution of the positive charge in 1+˙ calculated
by the PM3-UHF/RHF method, the stability of the aminated radicals formed by
the addition of NH3 to 1+˙ and the
stability of the aminated anion formed by the reduction of the aminated
radicals by DCB-˙. The stabilities of these
intermediates are estimated by the calculation of the heat of formation by
the PM3-UHF/RHF method. Distributions of the positive charge in
1+˙ and the stabilities of the aminated anion show a
good agreement with the product analysis.
Transition‐Metal‐Free Deconstructive Lactamization of Piperidines
作者:Julio Romero‐Ibañez、Silvano Cruz‐Gregorio、Jacinto Sandoval‐Lira、Julio M. Hernández‐Pérez、Leticia Quintero、Fernando Sartillo‐Piscil
DOI:10.1002/anie.201903880
日期:2019.6.24
piperidines through a dual C(sp3)–H oxidation, as transitory intermediates. Experimental and theoretical studies confirm that this unprecedented lactamization occurs in a tandem manner involving an oxidative deamination of 3‐alkoxyamino‐2‐piperidones to 3‐keto‐2‐piperidones, followed by a regioselective Baeyer–Villigeroxidation to give N‐carboxyanhydride intermediates, which finally undergo a spontaneous
Rh-Catalyzed [7 + 1] Cycloaddition of Buta-1,3-dienylcyclopropanes and CO for the Synthesis of Cyclooctadienones
作者:Zhong-Ke Yao、Jianjun Li、Zhi-Xiang Yu
DOI:10.1021/ol102700m
日期:2011.1.7
advance transition-metal-catalyzed cycloadditions for the synthesis of various-sized ring compounds. A new seven-carbon building block from buta-1,3-dienylcyclopropanes (BDCPs) has been developed, showing that, under the catalysis of [Rh(CO)2Cl]2, BDCPs react with CO to give [7 + 1] cycloaddition products, cyclooctadienones. The present [7 + 1] reaction provides an efficient entry to the synthetically