Synthesis of (E)- and (Z)-alpha-alkylidene-gamma-aryl-gamma-butyrolactones via alkenylalumination of oxiranes.
Alkenylalumination of substituted styrene oxides with [alpha-(ethoxycarbonyl)alkenyl]diisobutylaluminum, in the presence of BF(3).Et(2)O, affords the corresponding (Z)-alpha-alkylidene-gamma-aryl-gamma-hydroxy esters in 81-100% Z-selectivity. Chromatographic separation of isomers, followed by lactonization with trifluoroacetic acid, provides isomerically pure (Z)-alpha-alkylidene-gamma-aryl-gamma-butyrolactones in 53-78% overall yield. Isomerization of the (Z)-alkylidene hydroxyl esters using LDA, followed by protonation using a bulky proton source, such as BHT, provides a simple route to the corresponding alpha-(E)-alkylidene-gamma-phenyl-gamma-hydroxy esters in 72-78% yield, which were cyclized to obtain the corresponding (E)-butyrolactones in 78-85% yield.
Ramachandran
P Veeraraghavan
PV
Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907-2084, USA. chandran@purdue.edu
Garner
Garrett
G
Pratihar
Debarshi
D
D015107:4-Butyrolactone / Q000138:chemical synthesis / Q000737:chemistry*; D000478:Alkylation; D000537:Aluminum Oxide / Q000737:chemistry*; D003500:Cyclization; D005027:Ethylene Oxide / Q000737:chemistry*; D007536:Isomerism; D007783:Lactones / Q000737:chemistry; D015394:Molecular Structure; D010087:Oxides / Q000737:chemistry; D020058:Styrene / Q000737:chemistry
D007783:Lactones; D010087:Oxides; D020058:Styrene; D005027:Ethylene Oxide; D000537:Aluminum Oxide; D015107:4-Butyrolactone