Animesh Roy1, Bilal A Bhat1,2, Salvatore D Lepore1. 1. Department of Chemistry, Florida Atlantic University , Boca Raton, Florida 33431-0991, United States. 2. CSIR-Medicinal Chemistry Division, Indian Institute of Integrative Medicine , Sanatnagar, Srinagar-190005, India.
Abstract
Chiral ammonium salts were used to catalyze the isomerization of organomanganese-complexed alkynyl aldehydes to chiral allenal building blocks in moderate to good enantiomeric excesses. Normally, conjugated alkynyl aldehydes do not isomerize to their thermodynamically less stable allene isomers. However, with a manganese auxiliary in place to promote allene formation, asymmetric protonation of cumulenolate intermediates was realized using a variety of cinchonidinium salts in a weakly basic biphasic reaction system. Optimal results were realized using a novel cinchonidinium geranyl derivative with its C-9 hydroxyl group playing a crucial role in enantioselectivity.
Chiral ammonium salts were used to catalyze the isomerization of organon class="Chemical">manganese-complexed alkynyl aldehydes to chiral allenal building blocks in moderate to good enantiomeric excesses. Normally, conjugated alkynyl aldehydes do not isomerize to their thermodynamically less stable allene isomers. However, with a manganese auxiliary in place to promote allene formation, asymmetric protonation of cumulenolate intermediates was realized using a variety of cinchonidinium salts in a weakly basic biphasic reaction system. Optimal results were realized using a novel cinchonidinium geranyl derivative with its C-9 hydroxyl group playing a crucial role in enantioselectivity.
Authors: Kayli M Johnson; Matt S Rattley; Filippo Sladojevich; David M Barber; Marta G Nuñez; Anna M Goldys; Darren J Dixon Journal: Org Lett Date: 2012-05-01 Impact factor: 6.005