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Substituent‐Controlled Electrocyclization of 2,4‐Dienones: Synthesis of 2,3,6‐Trisubstituted 2 H ‐Pyran‐5‐carboxylates and Their Transformations
Author(s) -
Peng Wei,
Hirabaru Toshiaki,
Kawafuchi Hiroyuki,
Inokuchi Tsutomu
Publication year - 2011
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201100780
Subject(s) - chemistry , knoevenagel condensation , substituent , pyran , cycloaddition , alkyl , medicinal chemistry , adduct , stereochemistry , organic chemistry , catalysis
A facile access to 2,3,6‐trisubstituted 2 H ‐pyran‐5‐carboxylates is developed by employing 2‐alkyl‐2‐enals as reactants with acetoacetates. The reaction involves Knoevenagel condensation followed by a 6π‐electrocyclization, in which the presence of the C2 alkyl substituent in the enals favors the formation of ( E )‐Knoevenagel adducts for the ensuing electrocyclization. The resulting 2 H ‐pyrans are hydrogenated to form 3,4‐dihydro‐2 H ‐pyrans and converted into the endoperoxides by singlet‐oxygen cycloaddition.