E- or Z-selective Knoevenagel condensation of acetoacetic derivatives: effect of acylated substituent, that is, TEMPO and amines, as an auxiliary, and new accesses to trisubstituted E- and Z-2-alkenals and furans.
Knoevenagel condensation of O-acetoacetylTEMPOs (2,2,6,6-tetramethylpiperidine-1-oxyl) with aldehydes substituted with an electron-withdrawing group such as aromatic and heteroaromatic ones leads preferentially to E-adducts, while acylacetoamides including Weinreb amides produce Z-adducts, exclusively. These E- and Z-adducts are selectively converted to the corresponding (2E)- and (2Z)-2-hyroxyalkyl-2-alkenals, respectively, by stepwise reductions of the acyl group with DIBALH and then the carboxylic functions after protection of the hydroxy group. Transformation of the Knoevenagel products by taking advantage of the E-geometry to trisubstituted furans is also developed.
Inokuchi
Tsutomu
T
Department of Bioscience and Biotechnology, Faculty of Engineering, Okayama University, Tsushima-naka, Okayama 700-8530, Japan. inokuchi@cc.okayama-u.ac.jp
Kawafuchi
Hiroyuki
H
D000090:Acetoacetates / Q000737:chemistry; D000215:Acylation; D000447:Aldehydes / Q000737:chemistry; D000473:Alkanes / Q000737:chemistry*; D000588:Amines / Q000737:chemistry*; D003497:Cyclic N-Oxides / Q000737:chemistry*; D005663:Furans / Q000737:chemistry*; D006358:Hot Temperature; D015394:Molecular Structure; D010084:Oxidation-Reduction; D013237:Stereoisomerism
D000090:Acetoacetates; D000447:Aldehydes; D000473:Alkanes; D000588:Amines; D003497:Cyclic N-Oxides; D005663:Furans; C016635:acetoacetic acid; C003959:TEMPO