A broad range of readily accessible N-sulfonyl imines undergo olefination reaction with nonstabilized phosphonium ylides under mild conditions to afford an array of both Z- and E-isomers of 1,2-disubstituted alkenes, allylic alcohols, and allylic amines in good yields and with greater than 99 : 1 stereoselectivity.
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Catalytic, oxidant-free, direct olefination of alcohols using Wittig reagents.
Chem Commun (Camb)
May 2015
Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa, Japan 904-0495.
Reported here is the catalytic, acceptorless coupling of alcohols with in situ generated, non-stabilized phosphonium ylides to form olefins as major products. The reaction uses low catalyst loadings and does not require added oxidants. Hydrogenation of the product is minimized and the reaction leads to Z (aliphatic) or E (benzylic) stereospecificity.
View Article and Find Full Text PDFStereoselective syntheses of the antihistaminic drug olopatadine and its E-isomer.
J Org Chem
July 2012
Laboratory of Organic Chemistry, Faculty of Pharmacy, and Institute of Biomedicine (IBUB), University of Barcelona, Av. Joan XXIII s/n, 08028 Barcelona, Spain.
Practical stereoselective synthetic routes to the antihistaminic drug olopatadine and its E-isomer have been developed, the key steps being a trans stereoselective Wittig olefination using a nonstabilized phosphorus ylide and a stereoselective Heck cyclization. The stereoselectivity of the Wittig reaction depends on both the phosphonium salt anion and the cation present in the base used to generate the ylide.
View Article and Find Full Text PDFUnequivocal experimental evidence for a unified lithium salt-free Wittig reaction mechanism for all phosphonium Ylide types: reactions with β-heteroatom-substituted aldehydes are consistently selective for cis-oxaphosphetane-derived products.
J Am Chem Soc
June 2012
Centre for Synthesis and Chemical Biology, Conway Institute of Biomolecular and Biomedical Research, School of Chemistry and Chemical Biology, University College Dublin, Belfield, Ireland.
The true course of the lithium salt-free Wittig reaction has long been a contentious issue in organic chemistry. Herein we report an experimental effect that is common to the Wittig reactions of all of the three major phosphonium ylide classes (non-stabilized, semi-stabilized, and stabilized): there is consistently increased selectivity for cis-oxaphosphetane and its derived products (Z-alkene and erythro-β-hydroxyphosphonium salt) in reactions involving aldehydes bearing heteroatom substituents in the β-position. The effect operates with both benzaldehydes and aliphatic aldehydes and is shown not to operate in the absence of the heteroatom substituent on the aldehyde.
View Article and Find Full Text PDFTunable stereoselective alkene synthesis by treatment of activated imines with nonstabilized phosphonium ylides.
Chem Commun (Camb)
February 2011
Joint Laboratory of Green Synthetic Chemistry, Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, China.
A broad range of readily accessible N-sulfonyl imines undergo olefination reaction with nonstabilized phosphonium ylides under mild conditions to afford an array of both Z- and E-isomers of 1,2-disubstituted alkenes, allylic alcohols, and allylic amines in good yields and with greater than 99 : 1 stereoselectivity.
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