Synthesis of Enantiomerically Pure Allenes with Central and Axial Chirality Mediated by a Remote Sulfinyl Group
作者:José García Ruano、José Alemán、Vanesa Marcos
DOI:10.1055/s-0029-1217006
日期:2009.10
Enantiomerically pure 2-(p-tolylsulfinyl)benzylcopper reagents react with propargyl bromides and mesylates, affording enantiomerically pureallenes with central and axialchirality. Both regioselectivity (SN2′ processes) and configuration at the chiral axis are completely controlled by the sulfinylgroup. The stereoselectivity at the benzylic position is very high. Complete kinetic resolution and moderate
对映体纯的2-(对甲苯基亚磺酰基)苄基铜试剂与炔丙基溴和甲磺酸酯反应,得到具有中心和轴向手性的对映体纯的烯。区域选择性(S N 2'过程)和在手性轴上的构型均完全由亚硫酰基控制。在苄基位置的立体选择性非常高。可以实现外消旋炔丙基甲磺酸酯的完全动力学拆分和中等动态拆分。可以通过假设亚砜基氧使苄基铜稳定并作为分子内S N 2'亲核进攻的前一步,将三键与金属缔合来解释这种立体化学行为。 丙二烯-亚磺酰基-轴向手性-中心手性-不对称合成
Nickel-catalyzed coupling of terminal allenes, aldehydes, and silanes
作者:Sze-Sze Ng、Timothy F. Jamison
DOI:10.1016/j.tet.2006.05.006
日期:2006.12
The development of a nickel-catalyzedcoupling of terminal allenes, aldehydes, and silanes is described. This transformation selectively provides 1,1-disubstituted allylic alcohols, protected as a silyl ether. The choice of the reducing agent is essential for achieving selectivity in this coupling process. A trialkylphosphine (Cyp3P) and an N-heterocyclic carbene (IPr) are complementary in this reaction
Alkynylalanes were found to react efficiently with propargylic electrophiles, such as propargyl mesylates and propargyl diethylphosphates. The reaction proceeds with high regioselectivity and does not require copper or any other transition metal.
Approaches to diene based homopumiliotoxin alkaloids
作者:Helena McAlonan、David Montgomery、Paul J. Stevenson
DOI:10.1016/0040-4039(96)01564-x
日期:1996.9
Palladium catalysed reductive cyclisation of a 1,1-dibromoalkene to an acetylene gives the core unit of the quinolizidine based diene homopumiliotoxin alkaloids with complete control of stereochemistry of the exocyclic double bond.
Copper-Free Synthesis of Skipped Diynes via Cross-Coupling Reactions of Alkynylalanes with Propargylic Electrophiles
作者:Jilali Kessabi、Renaud Beaudegnies、Pierre M. J. Jung、Benjamin Martin、Florian Montel、Sebastian Wendeborn
DOI:10.1021/ol0623769
日期:2006.11.1
Alkynylalanes provide a new, copper-free route to skippeddiynes when combined with propargylic electrophiles bearing an aluminum-complexing leaving group. The reaction is mild, efficient, and, in contrast to copper-mediated methods, highly regioselective. [reaction: see text]