Benzo[ d ]oxazoles from Anilides by N -Deprotonation– O -S N Ar Cyclization.

Autor:	Nevels, Nash E., Subera, Luke, Bunce, Richard A.
Předmět:	ANILIDES ACETANILIDES OXAZOLES RECRYSTALLIZATION (Metallurgy) ACETANILIDE
Zdroj:	Molecules; Sep2024, Vol. 29 Issue 18, p4322, 20p
Abstrakt:	A synthesis of benzo[d]oxazoles by an N-deprotonation–O-SNAr cyclization sequence from anilide precursors is reported. Anilides derived from 2-fluorobenzaldehydes, activated toward SNAr ring closure by C5 electron-withdrawing groups, were prepared and subjected to deprotonation–cyclization using 2 equiv. of K2CO3 in anhydrous DMF. Following deprotonation at nitrogen, the delocalized anion cyclized from the amide oxygen to give high yields of benzo[d]oxazoles. The temperature required for the cyclization of benzanilides correlated with the potency of the C5 activating group on the SNAr acceptor ring with nitro (most potent) reacting at 90 °C (1 h), cyano reacting at 115 °C (1 h), methoxycarbonyl reacting at 120 °C (2 h), and trifluoromethyl (least potent) reacting at 130 °C (3 h). Acetanilides were more difficult to cyclize but generally required 4–6 h at these same temperatures for completion. Product purification was accomplished by recrystallization or chromatography. [ABSTRACT FROM AUTHOR]
Databáze:	Complementary Index
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