Access to Benzoxazepines and Fully Substituted Indoles via HDDA Coupling

Abstract

The HDDA-derived benzyne intermediate was captured by oxazolines based on the addition reaction of benzyne to the CN double bond. Benzoxazepine derivatives, fused benzoxazepine derivatives, and fully substituted indoles are synthesized in one step. The reaction does not require any catalyst or additives. Possible reaction mechanisms are presented.

Hexadehydro-Diels–Alder Reaction: Benzyne Generation via Cycloisomerization of Tethered Triynes

“…Zheng and co-workers have recently reported a thorough examination of the trapping of HDDA benzynes with oxazolines. Three variants of this chemistry, each producing a novel product architecture, are shown in Figure g–i . The nature of the substituent at the 2-position of the oxazoline is the key factor in determining the reaction pathway.…”

“…Three variants of this chemistry, each producing a novel product architecture, are shown in Figure 7g−i. 63 The nature of the substituent at the 2-position of the oxazoline is the key factor in determining the reaction pathway. The conversion of 28 to 60 (Figure 7g) shows that oxazolines bearing an alkyl substituent in their 2-position form azetidine and ring-opened o-quinomethide imines like XXXIIIa and XXXIIIb en route to product.…”

Epoxyanthracene Derivatives and Dicarbonylation on Benzene Ring via Hexadehydro-Diels–Alder (HDDA) Derived Benzynes with Oxazoles

“…The low temperature is unfavorable to the occurrence of the retro-Diels-Alder reaction to make the nitrile compounds leaving. Previously our group once reported the cycloaddition reaction between HDDA-derived benzyne [17][18][19] and imidazole, and accidentally obtained isoindole 1,3-dione compounds. Considering the different reactivity between HDDA-derived benzyne and traditional benzyne, we investigated the reaction results of HDDA-derived benzyne with oxazole compounds here.…”

Ring-Closure Mechanisms Mediated by Laccase to Synthesize Phenothiazines, Phenoxazines, and Phenazines

“…In addition, phenothiazines have been reported to possess multidrug resistance reverting activity. , Phenothiazines are also part of dyes such as methylene blue or act as electron donors in photovoltaic cells. , Phenoxazinones and phenazines can also be used in optoelectronics such as in organic light-emitting diodes. , Chemical methods to synthesize phenothiazines comprise catalyses with transition metals such as copper iodide, iron salt, or palladium in organic solvents and in part at elevated temperatures above 90 °C. − Alternatively, KI or Cs 2 CO 3 in organic solvents can be used. , The phenothiazines can be oxidized to the respective phenothiazinones, e.g., by K 2 Cr 2 O 7 or Na 2 Cr 2 O 7 in boiling acetic acid . Other biologically active heterocycles such as benzoxazepines can be synthesized in organic solvents at a temperature of 100 °C . The successful laccase-mediated synthesis of different substance classes (including in part also isomer formation) in comparison with traditional organic reactions catalyzed by oxidants such as silver oxide, sodium iodate, or manganese dioxide was described previously. ,− This recommends the laccase for various industrial applications. , …”

“…62 Other biologically active heterocycles such as benzoxazepines can be synthesized in organic solvents at a temperature of 100 °C. 63 The successful laccase-mediated synthesis of different substance classes (including in part also isomer formation) in comparison with traditional organic reactions catalyzed by oxidants such as silver oxide, sodium iodate, or manganese dioxide was described previously. 24,64−68 This recommends the laccase for various industrial applications.…”