2-Pyridylnitrene and 3-Pyridazylcarbene and Their Relationship via Ring-Expansion, Ring-Opening, Ring-Contraction, and Fragmentation

Precursors of 3-pyridylnitrene and 2- and 4-pyrimidinylcarbenes all afford mixtures of 2- and 3-cyanopyrroles on flash vacuum thermolysis, but 3-cyanopyrroles are the first-formed products. 3-Quinolylnitrenes and 4-quinazolinylcarbenes similarly afford 3-cyanoindoles. 2-Pyrimidinylcarbenes rearrange to 3-pyridylnitrenes, but 4-pyrimidinylcarbenes and 4-quinazolinylcarbenes do not necessarily rearrange to the corresponding 3-pyridylnitrenes or 3-quinolylnitrenes. The ring contraction reactions are interpreted in terms of ring opening of either the nitrenes or the diazacycloheptatetraenes to nitrile ylides.

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Synthesis and Antiproliferative Activity of Phosphorus Substituted 4-Cyanooxazolines, 2-Aminocyanooxazolines, 2-Iminocyanooxazolidines and 2-Aminocyanothiazolines by Rearrangement of Cyanoaziridines

Molecules ◽

10.3390/molecules26144265 ◽

2021 ◽

Vol 26 (14) ◽

pp. 4265

Author(s):

Victor Carramiñana ◽

Ana M. Ochoa de Ochoa de Retana ◽

Francisco Palacios ◽

Jesús M. de los de los Santos

Keyword(s):

Ring Opening ◽

Human Lung ◽

Ring Expansion ◽

Moderate Activity ◽

A549 Cell Line ◽

One Pot ◽

Acidic Conditions ◽

Lung Adenocarcinoma A549 ◽

High Yields

Several phosphorus-substituted N-acylated cyanoaziridines 2 and N-carbamoylated cyanoziridines 5 were prepared in good to high yields. N-Acylated cyanoaziridines 2 were used, after ring expansion, in an efficient synthesis of oxazoline derivative 3a and in a completely regio-controlled reaction in the presence of NaI. Conversely, N-carbamoyl cyanoaziridines 5 reacted with NaI to obtain a regioisomeric mixture of 2-aminocyanooxazolines 7. Mild acidic conditions can be used for the isomerization of N-thiocarbamoyl cyanoaziridine 6a into a 2-aminocyanothiazoline derivative 8a by using BF3·OEt2 as a Lewis acid. Likewise, a one pot reaction of NH-cyanoaziridines 1 with isocyanates obtained 2-iminocyanooxazolidines 9 regioselectively. This synthetic methodology involves the addition of isocyanates to starting cyanoaziridines to obtain N-carbamoyl cyanoaziridines 5, which after the ring opening, reacts with a second equivalent of isocyanate to give the final 2-imino cyanooxazolidines 9. In addition, the cytotoxic effect on the cell lines derived from human lung adenocarcinoma (A549) was also screened. 2-Iminooxazolidines 9 exhibited moderate activity against the A549 cell line in vitro. Furthermore, a selectivity towards cancer cells (A549) over non-malignant cells (MCR-5) was detected.

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Ring expansion and ring opening of 3-halooxindoles with N-alkoxycarbonyl-O-tosylhydroxylamines for divergent access to 4-aminoquinolin-2-ones and N-Cbz-N’-arylureas

Organic Chemistry Frontiers ◽

10.1039/d0qo01335h ◽

2021 ◽

Author(s):

Wei-Cheng Yuan ◽

Jian Zuo ◽

Shu-Pei Yuan ◽

Jian-Qiang Zhao ◽

Zhen-Hua Wang ◽

...

Keyword(s):

Ring Opening ◽

Ring Expansion

The reaction of N-alkoxycarbonyl-O-tosylhydroxylamines with indol-2-ones in situ generated from 3-halooxindoles has been developed for divergently accessing 4-aminoquinolin-2-ones and N-Cbz-N’-arylureas in good to excellent yields.

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N-Chlorinative Ring Contraction of 1,4-Dimethoxyphthalazines via a Bicyclization/Ring-Opening Mechanism

Synthesis ◽

10.1055/s-0040-1706639 ◽

2020 ◽

Author(s):

Jeong Kyun Im ◽

Ilju Jeong ◽

Jun-Ho Choi ◽

Won-jin Chung ◽

ByeongDo Yang ◽

...

Keyword(s):

Ring Opening ◽

Reaction Conditions ◽

Ring Contraction ◽

Silyl Group ◽

Favorskii Rearrangement ◽

Mechanistic Analysis ◽

Group A ◽

Overall Efficiency ◽

Trichloroisocyanuric Acid

AbstractAn unprecedented N-chlorinative ring contraction of 1,2-diazines was discovered and investigated with an electrophilic chlorinating reagent, trichloroisocyanuric acid (TCICA). Through optimization and mechanistic analysis, the assisting role of n-Bu4NCl as an exogenous nucleophile was identified, and the optimized reaction conditions were applied to a range of 1,4-dimethoxyphthalazine derivatives. Also, an improvement of overall efficiency was demonstrated by the use of a labile O-silyl group. A bicyclization/ring-opening mechanism, inspired by the Favorskii rearrangement, was proposed and supported by the DFT calculations. Furthermore, the efforts on scope expansion as well as the evaluation of other electrophilic promoters revealed that the newly developed ring contraction reactivity is a unique characteristic of 1,4-dimethoxyphthalazine scaffold and TCICA.

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A study of multiple ring expansion and ring contraction rearrangements in observable cycloalkyl cations

Journal of the American Chemical Society ◽

10.1021/ja00484a037 ◽

1978 ◽

Vol 100 (16) ◽

pp. 5134-5140 ◽

Cited By ~ 9

Author(s):

Roger P. Kirchen ◽

Ted S. Sorensen ◽

Kim E. Wagstaff

Keyword(s):

Ring Expansion ◽

Ring Contraction ◽

Multiple Ring

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Palladium-Catalyzed Ring-Contraction and Ring-Expansion Reactions of Cyclic Allyl Amines

Angewandte Chemie International Edition ◽

10.1002/anie.201100612 ◽

2011 ◽

Vol 50 (26) ◽

pp. 5924-5926 ◽

Cited By ~ 53

Author(s):

Igor Dubovyk ◽

Dmitry Pichugin ◽

Andrei K. Yudin

Keyword(s):

Ring Expansion ◽

Ring Contraction ◽

Palladium Catalyzed

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ChemInform Abstract: Synthesis of C-Furanosides from a D-Glucal-Derived Cyclopropane (I) Through a Ring-Expansion/Ring-Contraction Sequence.

ChemInform ◽

10.1002/chin.201119185 ◽

2011 ◽

Vol 42 (19) ◽

pp. no-no

Author(s):

Russell J. Hewitt ◽

Joanne E. Harvey

Keyword(s):

Ring Expansion ◽

Ring Contraction

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Heck-Type Coupling of Fused Bicyclic Vinylcyclopropanes: Synthesis of 1,2-Dihydropyridines, 2,3-Dihydro-1H-Azepines, 1,4-Cyclohexadienes, 2H-Pyrans, and 1,3-Butadienes

10.26434/chemrxiv.14731455 ◽

2021 ◽

Author(s):

Nikolai Wurzer ◽

Urszula Klimczak ◽

Tobias Babl ◽

Sebastian Fischer ◽

Ricardo A. Angnes ◽

...

Keyword(s):

Heck Reaction ◽

Ring Opening ◽

Theoretical Calculations ◽

Ring Expansion ◽

Mechanistic Studies ◽

Type Coupling ◽

Hydride Elimination ◽

Unexpected Behavior

Herein, we report a versatile approach for the endocyclic ring-opening of bicyclic vinylcyclopropanes triggered by Heck arylations. Key step for this transformation is a [1,3]-migratory shift of Pd allowing the ring expansion of cyclopropanated pyrroles, piperidines, furans as well as cyclopentadienes to grant access to the corresponding 1,2-dihydropyridines, 2H-pyrans, 2,3-dihydro-1H-azepines and 1,4-cyclohexadienes, respectively. Additionally, gem-disubstituted cyclopropanated furans showed unexpected behavior by giving diastereoselectively asymmetrically substituted dienes. Mechanistic studies and theoretical calculations point towards a facile [1,3]-migratory shift of Pd along the cyclopropane moiety, which can successfully compete with the usual termination step of a Heck reaction via a syn-b-hydride elimination.

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