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Inter‐ and intramolecular hetero diels‐alder reactions, 41. Unusual stereocontrol in intramolecular hetero diels‐alder reactions of 2‐Aza‐1,3‐butadienes. A stereoselective sequential synthesis of annulated tetrahydropyridines
Author(s) -
Tietze Lutz F.,
Utecht Jens
Publication year - 1992
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19921251014
Subject(s) - chemistry , intramolecular force , moiety , stereoselectivity , selectivity , diels–alder reaction , stereochemistry , yield (engineering) , intramolecular reaction , cycloaddition , organic chemistry , catalysis , materials science , metallurgy
Condensation of aldehydes 1a–e with 5‐amino‐3‐methylisoxazole ( 4 ) gives the corresponding imines 5a–e with a 2‐aza‐1,3‐butadiene moiety, which cyclize selctively, e.g. 5a to form the trans ‐fused tetrahydropyridine 7a and 5c to yield the cis ‐fused cycloadduct 8c . The astounding difference in the selectivity of these reactions is explained by electronic effects and suggests a change in the dominating interactions of the orbitals in the transition structure. The structure of 7a is elucidated by an X‐ray analysis.