Synthesis of 1H-1-benzazepines by thermolysis of 2a,7b-dihydro-3H-cyclobut[b]indoles

Ikeda, Masazumi; Ohno, Katsuhito; Takahashi, Masami; Uno, Toshiko; Tamura, Yasumitsu; Kido, Masaru

doi:10.1039/p19820000741

Cited by 30 publications

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“…1-Benzoyl-2,3,4,5-tetrahydro-1 H -1-benzazepine (11). Yield: 90% as colorless, needlelike crystals, R f = 0.26, hexanes/EtOAc (3/1); mp 94.2−95.4 °C (from Et 2 O/hexanes; lit . 86−87 °C, from n -hexane).…”

Section: Methodsmentioning

confidence: 99%

Conformation Analyses, Dynamic Behavior and Amide Bond Distortions of Medium-sized Heterocycles. 1. Partially and Fully Reduced 1-Benzazepines

et al. 2005

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Five 1-benzazepine heterocycles were synthesized by utilizing transition-metal-catalyzed processes in key bond-forming steps. exo-Methylene and methyl substituents were introduced at position 5, as well as a unit of unsaturation between positions 3 and 4, with benzoyl or benzyl N-substituents. Solution- and solid-state structures were examined, using dynamic NMR spectroscopy and X-ray crystallography, corroborated by molecular mechanics calculations. Greater amide distortion is associated with a more stable ground-state structure, which is in turn more reluctant to undergo conformational changes.

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Section: Methodsmentioning

confidence: 99%

Conformation Analyses, Dynamic Behavior and Amide Bond Distortions of Medium-sized Heterocycles. 1. Partially and Fully Reduced 1-Benzazepines

et al. 2005

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“…Diinserted [ C , N ] palladacycles upon depalladation or the reaction of cyclopalldated [κ 2 ( C , N )PdL 2 ] + [WCA] − with 2 equiv of alkynes are, on the basis of the literature, anticipated to afford (i) heterocycles wherein the butadienyl unit possesses cis , cis stereochemistry, (ii) heterocycles with a cyclobutene unit , (see structures A and B in Chart ), and (iii) heterocycles with unanticipated frameworks. , The heterocycles A and B are considered as valence isomers; the thermal conversion of the latter to the former , is known in the literature, and thermal conversion of the former to the latter has been proposed in the literature . The formation of a heterocycle such as 3 which possesses the framework A in the depalladation reaction of diinserted [ C , N ] palladacycles has never been reported in the literature, although Pfeffer and co-workers erroneously claimed the formation of azacyclooctatriene from depalladation of a diinserted [ C , N ] palladacycle; later this compound turned out to be a benzofulvene derivative, as has been proven by Heck and co-workers through a structural determination .…”

Section: Resultsmentioning

confidence: 99%

Depalladation of Neutral Monoalkyne- and Dialkyne-Inserted Palladacycles and Alkyne Insertion/Depalladation Reactions of Cationic Palladacycles Derived from N,N′,N″-Triarylguanidines as Facile Routes for Guanidine-Containing Heterocycles/Carbocycles: Synthetic, Structural, and Mechanistic Aspects

2014

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Depalladation of the monoalkyne-inserted cyclopalladated guanidines [κ 2 (C,N)Pd(2,6-Me 2 C 5 H 3 N)Br] (I and II) in PhCl under reflux conditions and that of the dialkyne-inserted cyclopalladated guanidine [κ 2 (C,N):η 2 (CC)PdBr] (III) in pyridine under reflux conditions afforded a guanidine-containing indole (1), imidazoindole (2), and benzazepine (3) in 80%, 67%, and 76%, yields, respectively. trans-[L 2 PdBr 2 ] species (L = 2,6-Me 2 C 5 H 3 N, C 5 H 5 N) were also isolated in the aforementioned reactions in 35%, 42%, and 40% yields. Further, the reaction of the cyclopalladated guanidine [κ 2 (C,N)Pd(μ-Br)] 2 (IV) with AgBF 4 in a CH 2 Cl 2 /MeCN mixture afforded the cationic pincer type cyclopalladated guanidine [κ 3 (C,N,O)Pd(MeCN)][BF 4 ] (4) in 85% yield and this palladacycle upon crystallization in MeCN and the reaction of [κ 2 (C,N)Pd(μ-Br)] 2 (V) with AgBF 4 in a CH 2 Cl 2 /MeCN mixture afforded the cationic palladacycles [{κ 2 (C,N)Pd(MeCN) 2 ][BF 4 ] (5 and 6) in 89% and 91% yields, respectively. The separate reactions of 4 with 2 equiv of methyl phenylpropiolate (MPP) or diphenylacetylene (DPA) and the reaction of 5 with 2 equiv of MPP in PhCl at 110 °C afforded the guanidine-containing quinazolinium tetrafluoroborate 7 in 25−32% yields. The reaction of 6 with 2 equiv of DPA under otherwise identical conditions afforded the unsymmetrically substituted guanidinium tetrafluoroborate 8, containing a highly substituted naphthalene unit, in 82% yield. Compounds 1−8 were characterized by analytical and spectroscopic techniques, and all compounds except 4 were characterized by single-crystal X-ray diffraction. The molecular structures of 2 and 3 are novel, as the framework in the former arises due to the formation of two C−N bonds upon depalladation while the butadienyl unit in the latter revealed cis,cis stereochemistry, a feature unprecedented in alkyne insertion chemistry. Plausible pathways for the formation of heterocycles/carbocycles are proposed. The influence of substituents on the aryl rings of the cyclopalladated guanidine moiety and those on alkynes upon the nature of the products is addressed. Heterocycles 1 and 7 revealed the presence of two rotamers in about a 1.00:0.43 ratio in CDCl 3 and in about a 1.00:0.14 ratio in CD 3 OD, respectively, as detected by 1 H NMR spectroscopy while in CD 3 CN and DMSO-d 6 (1) and CD 3 CN and CDCl 3 (7), these heterocycles revealed the presence of a single rotamer. These spectral features are attributed to the restricted C−N single-bond rotation of the CN 3 unit of the guanidine moiety, which possibly arises from steric constraint due to the formation of a N−H•••Cl hydrogen bond with CDCl 3 (1) and N−H•••O and O−D•••O hydrogen bonds with CD 3 OD (7).

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Gadolinium Photocatalysis: Dearomative [2+2] Cycloaddition/Ring‐Expansion Sequence with Indoles

Schäfers

Daniliuc

et al. 2020

Angewandte Chemie

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Lanthanide photocatalysts are muchless investigated in synthetic chemistry than rare and expensive late transition metals.W eh erein introduce Gd III photocatalysis of ah ighly regioselective,i ntermolecular [2+ +2] photocycloaddition/ringexpansion sequence with indoles,w hich could provide divergent access to cyclopenta[b]indoles and indolines.Asimple and commercially available Gd(OTf) 3 salt is sufficient for this visible-violet-light-induced transformation. The reaction proceeds either through atransient or start-to-end dearomatization cascade and shows excellent regioselectivity (usually > 95:5 r.r.), broad scope (59 examples), good functional group tolerance and facile scale-up under mild, direct visible-lightexcitation conditions.M echanistic investigations reveal that direct excitation of the Gd(OTf) 3 /indole mixture gives an excited state intermediate,w hich undergoes the subsequent [2+ +2] cycloaddition and cyclobutane-expansion cascade. Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

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Synthesis of 1H-1-benzazepines by thermolysis of 2a,7b-dihydro-3H-cyclobut[b]indoles

Cited by 30 publications

References 0 publications

Conformation Analyses, Dynamic Behavior and Amide Bond Distortions of Medium-sized Heterocycles. 1. Partially and Fully Reduced 1-Benzazepines

Conformation Analyses, Dynamic Behavior and Amide Bond Distortions of Medium-sized Heterocycles. 1. Partially and Fully Reduced 1-Benzazepines

Gadolinium Photocatalysis: Dearomative [2+2] Cycloaddition/Ring‐Expansion Sequence with Indoles

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