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Reactions of 2‐aminooxazoles and 2‐aminothiazoles with dienophiles. Isolation of stable diels‐alder adducts
Author(s) -
Crank George,
Khan Humaid R.
Publication year - 1985
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570220527
Subject(s) - chemistry , adduct , oxazole , dimethyl acetylenedicarboxylate , diazepine , thiazole , yield (engineering) , diels–alder reaction , tropone , pyridine , pyrimidine , medicinal chemistry , organic chemistry , ring (chemistry) , cycloaddition , stereochemistry , catalysis , materials science , metallurgy
Room temperature reaction of 2‐aminooxazole 1 and its 4‐ and 4,5‐substituted derivatives, with dimethyl acetylenedicarboxylate gave good yields of Diels‐Alder adducts 2 , isolated as stable crystalline compounds. A competing process produced oxazole[3,2‐ a ]pyrimidines 3 , also in good yield. Minor products were also identified. 2‐Amino‐4‐methylthiazole ( 6 ) reacted in a similar manner and gave the Diels‐Alder adduct 7 and a thia‐zolo[3,2‐ a ]pyrimidine 8 as main products with a lesser amount of a thiazole [3,2‐ d ][1:3]diazepine ( 9 ). The aminooxazoles reacted with olefinic dienophiles to give pyridine derivative, formed by breakdown of the original unstable adducts.