Approach to Spirocyclohexadienimines and Corresponding Dienones through RadicalipsoCyclization onto Aromatic Azides (original) (raw)
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Al-Azhar Bulletin of Science, 2016
The spirooxindolo pyrrolidine frameworks form core units of many naturally occurring molecules possess significant pharmacological activities. The [3+2] cycloaddition reactions of azomethine ylides has been realized through multi-component reaction (MCR) affording regiospecific spiroindoline-3, 2'-pyrrolidine derivatives. The reactivity of the spiroindoline (increase E HOMO value) has been depended upon electron repelling and attracting groups. The behavior of spiroindoline towards carbon electrophile and nitrogen nucleophile can be investigated. All compound structures are fully supported by spectroscopic data and elemental analysis.The antioxidant activity for these synthesized compounds could be expected that highly antioxidant activity was with compounds which proved to possess high HOMO values
Molecules
Spirocyclic nitroxyl radicals (SNRs) are stable paramagnetics bearing spiro-junction at α-, β-, or γ-carbon atom of the nitroxide fragment, which is part of the heterocyclic system. Despite the fact that the first representatives of SNRs were obtained about 50 years ago, the methodology of their synthesis and their usage in chemistry and biochemical applications have begun to develop rapidly only in the last two decades. Due to the presence of spiro-function in the SNRs molecules, the latter have increased stability to various reducing agents (including biogenic ones), while the structures of the biradicals (SNBRs) comprises a rigid spiro-fused core that fixes mutual position and orientation of nitroxide moieties that favors their use in dynamic nuclear polarization (DNP) experiments. This first review on SNRs will give a glance at various strategies for the synthesis of spiro-substituted, mono-, and bis-nitroxides on the base of six-membered (piperidine, 1,2,3,4-tetrahydroquinoline...
HETEROCYCLES, 2008
The addition of benzophenone to a FeCl:/CHzClz mixture in the presence of 3',4'-dimethoxy-2-acetamidostilbene 17 unexpectedly leads to a dramatic improvement in yield of the indoline 20 from 38% (previously reported by us) to 75.4Yo, after careful examination of a variety of reaction conditions. A catalytic cycle has been proposed that involves not only stilbene radical cations but also Fe2n promoted benzophenone ketyl radical formation which enhances cyclisation, suppresses dimerization and accounts for the vinually quantitative recovery of the benzophenone. With the publication of a major review,' the bisindolines will continue to be in the forefront of research in the natural product/synthetic organic area. Malaysian Psychotria rostrata has brought forth bisindolines (specifically the pyrroloindoline structures) such as hodgkinsine, (-)-calycanthine, (+)-chimonanthine and calycosidine.2 Hodgkinsine A, for example, has demonstrated cytotoxic activify against Vero African green monkey kidney cells.3 Although recent reviews on synthetic methodology have perhaps given more attention to indole construction, Takayama's synthesis of meso-chimonanthine 3 from the tryptamine 1 and2 by exploitation of PIFA in CF:CHzOHa is significant (Scheme l). The same transformation can be achieved all be it in lower yield by use of thallium trifluoroacetate.t Although Takayama did not discuss the mechanism of these intriguing transformations in his original paper, we believe these results can be explained by a radical cationic cascade6 process promoted by phenyl iodine bistrifluoroacetate (PIFA). L"y' has exploited solid supported phenyliodine diacetate in the construction of a spirocyclic cyclohexadienone in which radical*cations (single electron transfer) were invoked. Since the chemistry depicted in Scheme I has mechanistic implications for our own studies to be described later, we will
Oxidative Ring Expansion of Spirocyclic Oxindole Derivatives
The Journal of Organic Chemistry, 2014
Oxidation of the spirocyclic oxindole derivative, isamic acid 1, led to decarboxylation and ring expansion to quinazolino[4,5-b]quinazoline-6,8-dione 7 rather than, as previously believed, its isomer 6. The structure of 7 was confirmed by X-ray crystallography. Condensation of isatin (indole-2,3-dione) and 2-aminobenzamide led to the spirocyclic molecule, spiro[3H-indole-3,2′(1H)quinazoline]-2,4′(1H,3H)dione 8, which was also identified as an intermediate in the oxidation of isamic acid. Mild hydrolysis of 7 gave the 10-membered molecule 22. Isamic acid could easily be converted to N-nitrosoisamic acid, which when heated in ethanol underwent a ring expansion to a hydroximino derivative, 38, of compound 6. The structure of 38 was confirmed by X-ray crystallography.
Radical-mediated cyclization reactions leading to spiro and [6,6]-fused heterocycles
Canadian Journal of Chemistry-revue Canadienne De Chimie, 2007
Regiochemical study of n Bu 3 SnH-AIBN-mediated aryl-radical cyclization of different 3-(2-bromophenylsulfenylmethyl)coumarins, 3-(2-bromophenylsulfonyl-methyl)coumarins, and 6-[(2-bromophenoxy)methyl]-4-methoxypyran-2-ones have been investigated with the formation of different [6,6]-fused and spirocylic heterocycles. The sulfides and ethers were prepared from 3-chloromethyl coumarin and 6-(bromomethyl)-4-methoxy pyran-2-one with different 2bromothiophenol and 2-bromophenols under classical alkylation condition. The corresponding sulfones were prepared by oxidation of the sulfides with m-CPBA.