127616-47-1Relevant articles and documents
Stereoselective Synthesis of Pyrrolizidine Alkaloids via Substituted Nitrones
Lathbury, David,Gallagher, Timothy
, p. 1017 - 1018 (1986)
The 3,5-disubstituted pyrrolizidine alkaloid (8) has been synthesised using, as a key step, the cyclisation of the allenic oxime E-(3) to generate a 5-substituted nitrone (4); under the same cyclisation conditions Z-(3) reacts via oxygen to give (9).
Highly stereoselective lodolactonization of 4,5-allenoic acids - An efficient synthesis of 5-(1′-Iodo-1′(Z)-alkenyl)-4,5-dihydro-2(3H)- furanones
Jiang, Xinpeng,Fu, Chunling,Ma, Shengming
supporting information; experimental part, p. 9656 - 9664 (2009/12/01)
In this paper, it is reported that the efficient iodolactonization 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)-furanones highly stereo-selectively. However, the reaction of axially optically active 4,5-allenoic acids (R)-(-)-5a and (R)-(-)-5b with I2 afforded the corresponding products with a serious loss of chirality. This problem was solved by conducting the iodolactonization with N-iodosuccinimide in CH2Cl2 in the presence of Cs 2CO3; however, the Z/E selectivity is somewhat lower. The pure optically active Z products were prepared by subsequent kinetic resolution with Sonogashira coupling. The reaction of thesubstrates with a substituent at the 3-position of the starting 4,5-allenoic acids afforded the trans-4,5-disubstituted γ-butyrolactones as the only products. The reaction of the 4,5-allenoic acids (S)-(+)-11, (R)-(-)-11, and (S)-(+)-lm with a center chirality at the 3-position afforded the trans products with very high enantiopurity and up to 98:2 Z/E selectivity regardless of the axial chirality of the allene moiety.
