Enediynes heterocyclic

Suzuki, I. Shigenaga, A. Nemoto, El. Shibuya, M. Acid-catalysed cycloaromatization of enediyne model compounds via enyne-allene intermediates. Heterocycles 2001, 54, 571-576. 

Changing the reactivity of heterocyclic enediynes by metal-ion coordination 00EJO381. 

While most attention has been directed towards the preparation of carbocyclic enediynes, ten-membered heterocyclic enediynes... 

Design, synthesis, and biological activity of urmatural enediynes (including those with heterocyclic fragments) and related analogs equipped with pH-dependent or phototriggering devices 07CRV2861. 

Design and synthesis of heterocycle-fused enediyne prodrugs activable at will 06ARK(7)261. 

Nucleophihc cychzations of enediynes as a method for polynuclear heterocycle synthesis 12KGS87. 

Cyclizations of enediynes under the action of electrophiles 13KGS129. Cyclization reactions of l,l-bis(trimethylsilyloxy)ketene acetals (synthesis of lactones, cyclic anhydrides, lactone-bridged N-heterocycles, lactone-annulated N-heterocycles) 12SL1283. 

Interestingly, when the substrate was switched from benzene-1,2-dialkyne 90 to cA-enediyne 95, 6-endo-dig cyclization reaction pathway was observed. Two regioisomeric ort/zo-auroaryl cation intermediates 96 and 98 were proposed via dual gold-catalyzed 6-endo-dig cyclization model, which can be mutual isomerization via aryne-coordinated gold complex 97. Ort/zo-aurophenyl cation intermediates 98 could be trapped by a tethered hydroxy or sulfonamide group to deliver the seven-membered O- or AT-heterocycles 99 (Scheme 12.45) [48]. 

Many of these reactions have attracted the attention of researchers due to the fact that these processes occur in the body during the application of anticancer drugs containing an enediyne block. Chapter 3 is devoted mainly to the analysis of papers related to the study of the cyclization mechanism. Chapter 4 includes additional material on cycloaddition with acetylenic units or those sourced from acetylenic compounds, leading to the formation of carbo- and heterocycles of different structures. The concluding Chapter 5 includes some recent results. 

In this chapter, we also evaluate the application polyalkyne and enediyne azamacrocyclic systems [177,182,183]. Since the macrocyclic systems include a nitrogen atom between multiple bonds, their [2-1-2- -2] cycloaddition reactions represent a route to the structures with the polycyclic aza-heterocycles. 

The main use of this reaction is for the synthesis of bowl-shaped polycyclic aromatic hydrocarbons and fullerenes [325], Exploring the boundaries of these reactions resulted in the synthesis of compounds of different geometry, tt-electron structure, aromaticity, and with the presence of heteroatoms [324]. Various cross-conjugated enediynes exert anionic cycloaromatization to form fulvene and fulvalene anions and even heterocycles. In accordance with the concept of aromaticity, the anionic Bergman type cyclization is preferred to the classical Bergman cycloaromatization of linear enediynes. This anionic cyclization differs considerably from the classical Bergman cyclization and related cycliza-tions, as well as from other dianionic cyclizations [326]. 

Spontaneous cyclization of enediynes can occur as a click reaction via the formation of triazine ring. The cycloaromatization of a nonaryl enediyne occurs after its reaction with sodium azide. The azide 3.727 rearranges spontaneously to enyne-allene 3.728. The consecutive Myers-Saito cycloaromatization, involving diradical 3.729, leads to the heterocyclic product 3.730 (Scheme 3.83) [336]. Since the mechanism involves the formation of diradical 3.729 in ambient conditions, it can be used for the DNA cleavage. So, the enediyne 3.727 at 37°C for 4 hours cuts the single-stranded helix of a supercoiled DNA plasmid (pBR 322). 

Dipolar cycloaddition to alkenes and alkynes leads to the formation of condensed heterocycles. Various heterocycles such as imines, aziridines, and pyrrolidines were produced using an alkene as a dipo-larophile [336]. The studies on cycloaromatization have focused on the design of the enediynes and non-thermal routes of cycloaromatization. Some examples of nonradical cycloaromatization have been considered above. Cyclization of this type create a methodology for the synthesis... 

To study the effect of the cinnoline heterocycle on the reactivity of 10-membered enediynes, the rates of Bergman cyclization of compound 3.824 and 3,4-benzocyclodeca-l,5-diyne-7-ol 3.827 were compared at 75°C in 2-propanol. The products were analyzed by high-performance liquid chromatography (HPLC). The reaction obeys first-order kinetics and enediyne 3.824 is four orders of magnitude more active than benzo-fused analog 3.827 [381a]. 

Tuesuwan, B. and Kerwin, S.M. (2006) 2-alkynyl-N-propargyl pyridinium salts pyridinium-based heterocyclic skipped aza-enediynes that cleave DNA by deoxyri-bosyl hydrogen-atom abstraction and guanine oxidation. Biochemistry, 45(23), 7265-7276. 

The monograph presents a modern methodology of regioselective synthesis of aromatic and nonaromatic carbocyclic and heterocyclic ring systems based mainly on [2+2+2] and [4+2] cycloaddition, and other reactions of acetylenic units, including enediynes and enyne-allenes. The features of the construction of polyaromatic structures, including heterostructures, based on cycloaddition reactions is used in the synthesis of advanced materials including nanomaterials. 

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