Gorlos-phos: addressing the stereoselectivity in palladium-catalyzed exo-mode cyclization of allenes with a nucleophilic functionality
作者:Juntao Ye、Suhua Li、Shengming Ma
DOI:10.1039/c3ob40983j
日期:——
A novel catalyst system has been indentified for addressing the long-standing issue of Z/E stereoselectivity in palladium-catalyzed exo-mode cyclization reactions of allenes bearing a nucleophilic functionality with organic halides or their equivalents. The readily accessible, sterically hindered monophosphine ligand Gorlos-Phos·HBF444 imparts a remarkable stereocontrolling ability with broad generality under Pd catalysis.
Highly Stereoselective Iodolactonization of 4,5-Allenoic Acids-An Efficient Synthesis of 5-(1′-Iodo-1′(<i>Z</i>)-alkenyl)-4,5-dihydro-2(3<i>H</i>)-furanones
作者:Xinpeng Jiang、Chunling Fu、Shengming Ma
DOI:10.1002/chem.200801363
日期:2008.10.29
In this paper, it is reported that the efficientiodolactonization of 4,5-allenoic acid with I2 in cyclohexane in the presence or absence of K2CO3 afforded 5-(1'-iodo-1'(Z)-alkenyl)-4,5-dihydro-2(3H)-furanoneshighlystereoselectively. However, the reaction of axially optically active 4,5-allenoic acids (R)-(-)-5 a and (R)-(-)-5 b with I2 afforded the corresponding products with a serious loss of chirality
Highly Regio- and Stereoselective Cyclic Iodoetherification of 4,5-Alkadienols. An Efficient Preparation of 2-(1′(<i>Z</i>)-Iodoalkenyl)tetrahydrofurans
作者:Bo Lü、Xinpeng Jiang、Chunling Fu、Shengming Ma
DOI:10.1021/jo802079b
日期:2009.1.2
In this paper, an efficient way to synthesize 2-(1'(Z)-iodoalkenyl)tetrahydrofurans from 4,5-alkadienols and 12 was developed. The reaction of the 4,5-allenols with a substituent in the 3-position afforded the trans-2,3-disubstituted tetrahydrofurans with very high diastereoselectivity. However, when the axially optically active 4,5-allenol was treated with 12 in n-hexane, the efficiency for chirality transfer was low. This problem was circumvented by conducting the reaction in CH2Cl2 at room temperature and applying N-iodosuccinimide as the electrophilic reagent; however, the Z/E ratio for the products is much lower. Highly optically active Z-products may be prepared via the kinetic resolution via a Sonogashira coupling reaction with propargyl alcohol.