Synthesis of dibenzo[b,f][1,4]oxazepin-11(10H)-one and pyrido[2,3-b][1,4]benzoxazepin-10(11H)-one compounds based on o-nitrochloro derivatives of benzene and pyridine

Efficient Use of 1,2‐Dihaloazine Synthons in Transition‐Metal‐Free Preparation of Diverse Heterocycle‐Fused 1,4‐Oxazepines

“…Although the yields of the condensation products did not exceed 60 %, we found the initial conditions to be optimal in terms of yield and ease of product purification (all attempts to alter the reaction conditions only worsened the preparative outcome of these reactions). Products 7a – 7d were distinctly more soluble than the polycyclic 1,4‐oxazepines that we had previously studied,3–5 as was expected from the presence of the tertiary amine solubilizing side chains and the fused azine moiety. In all cases, it was not feasible to isolate the product by precipitation from the aqueous medium.…”

“…The conditions that we previously used for the preparation of the products in Figure 1 (i.e., K 2 CO 3 , DMF, 80 °C)3–5 could be employed in the condensations of 4 , 5a , and 5b with pyrazolyl phenols 3 (see Scheme ). Although the yields of the condensation products did not exceed 60 %, we found the initial conditions to be optimal in terms of yield and ease of product purification (all attempts to alter the reaction conditions only worsened the preparative outcome of these reactions).…”

“…This was only achieved by chromatography after an extractive workup. The regiochemistry of products 7b – 7e was determined (see Scheme ) from the known mode of reactivity for the pyrazolyl phenols (phenolate first) and the 4,5‐dichloro‐3(2 H )‐pyridazinones (Cl at the 5‐position first) as well as the fact that the Smiles rearrangement had been observed in all similar condensations that we have studied3–5 and is well‐documented for 4,5‐dichloro‐3(2 H )‐pyridazinone substrates 16–18. (The universal character of the Smiles rearrangement that takes place in these condensations was further confirmed by X‐ray analysis of a new condensation product as described below.…”

“…Upon being exposed to potassium carbonate in N , N ‐dimethylformamide (DMF) at 80 °C, the corresponding pairs provide easy one‐step access to various tri‐ and tetracyclic 1,4‐oxazepines (see Figure 1). 3–5 The attractive features of this approach include not only its practical simplicity but also its unequivocal regiochemical outcome. In all of the examined cases, the reactions were initiated by the phenoxide anion displacing the halogen group from the S N Ar partner accompanied by a Smiles rearrangement6 and concluded by a denitrocyclization reaction.…”

Convenient Assembly of Privileged (Hetero)Arene‐Fused Benzo[1.4]oxazepines by Two Tandem SNAr Events. Part 2 – The Use of o‐[N‐(Hetero)aryl]aminomethyl Phenols

“…The approach is rather universal for phenols substituted at the ortho ‐position with a nucleophilic “Y‐Z‐H” motif which can be activated by deprotonation in the course of the reaction. So far, we have shown it to be applicable to the one‐step synthesis of carba‐ and aza‐versions of dibenzo[ b,f ][1,4]oxazepin‐11(10 H )‐ones ( 3a ), dibenzo[ b,f ]pyrazolo[1,5‐ d ][1,4]oxazepines ( 3b ), 2,3‐dihydrodibenzo[ b,f ]imidazo[1,2‐ d ][1,4]oxazepines ( 3c ), dibenzo[ b,f ][1,4,5]oxathiazepine 5,5‐dioxides ( 3d ), 10‐alkoxydibenzo[ b,f ][1,4]oxazepin‐11(10 H )‐ones ( 3e ), and 10‐carbonyl dibenzo[ b,f ][1,4]oxazepines ( 3f ) (Scheme ).…”