Mechanism of Alkaline Cyclization of 2-(Substituted benzamido)benzamides to 4-Quinazolinones
摘要:
The title amides cyclize rapidly to the corresponding quinazolin-4-ones in aqueous alkaline solution at 25 degrees C; the pseudo-first-order rate constants fit the empirical equation k(obs) = k(max) [OH-]/K-m + [OH-] + [OH-]K-2(m')) where K-m' is essentially zero for all except the 4-nitro species. The value of K-m measures the ionization of the neutral amide 1 to nonproductive conjugate base 2. Studies of the cyclization in alkali of 2-benzamido-N-methylbenzamide (1i) and 2-(N-methylbenzamido)benzamide (1j) indicate that 7 carries over 99% of the reaction flux and that the tautomer 8 does not contribute significantly. The ratio k(max)/K-m, is a composite rate constant first order in 1 and first order in [OH-]. The value of the Hammett rho for k(max)/K-m (0.67) is consistent with the above scheme where decomposition of 7 is rate limiting.
A [Cp*RhIII]‐catalyzed direct C−H amidation is carried out in ionic liquid. Both C(sp2)−H bonds of (hetero)arenes and alkenes and unactivated C(sp3)−H bonds can be easily amidated with high functional‐group tolerance and excellent yields under these conditions. Notably, using [Cp*RhIII]/[BMIM]BF4 (BMIM=1‐butyl‐3‐methylimidazolium) as the green and recyclable medium is environmentally benign, in light
[Cp * Rh III ]催化的直接CHH酰胺化反应在离子液体中进行。在这些条件下,(杂)芳烃和烯烃的C(sp 2)-H键和未活化的C(sp 3)-H键都容易被酰胺化,具有很高的官能团耐受性和优异的收率。值得注意的是,考虑到诸如昂贵的铑催化剂的可重复使用性等特性,使用[Cp * Rh III ] / [BMIM] BF 4(BMIM = 1-丁基-3-甲基咪唑鎓)作为绿色且可回收的介质对环境无害。避免剧毒的有机溶剂,温和的反应条件以及较短的反应时间。
Synthesis and rearrangement of 4-imino-4H-3,1-benzoxazines