Fused Heterocyde

It has been shown that, on treatment with base, 1-aminopy-ridinium iodide undergoes 1,3-dipolar addition with ethyl propiolate or dimethyl acetylenedicarboxylate thus the N-aminoheterocycles may serve as convenient starting materials for the synthesis of a variety of unusual fused heterocydes. ... 

The formation of an iminium salt via Michael addition between an azine and an electron-poor olefin was nicely exploited by Mironov et al. for the development of a three-component synthesis of benzo-fused heterocydes (95) (Scheme 5.28) [53], In this case, the intermediate 96 underwent a formal [4+1] cycloaddition with isocyanide that led to the observed heterocycle 95. 

Kim, D. et al. (2005) Potent 1,3,4-trisubstituted pyrrolidine CCR5 receptor antagonists effects of fused heterocydes on antiviral activity and pharmacokinetic properties. Bioorgank Medkirud Chemistry Letters, 15 (8), 2129-2134. 

Chaiand Lautens [158] reported in 2009 an elegant tandem Pd-catalyzed Suzuki-Miyaura/direct arylation reaction (Scheme 1.48). A wide range of aryl, alkenyl, and alkyl boronic acids were screened. The reactions were performed using e/w-dibromovinyl substrates, which were catalyzed by SPhos, and gave JV-fused heterocydes. Water was found to accelerate the reaction. The mechanism is quite involved, and we will not go into it here, but first indications are that the Suzuki-Miyaura reaction occurring before the direct arylation. 

Table 4 Conformational Properties of Some Angularly Fused Dibenzo Heterocydes...

The emission color of PAVs depends crucially on the nature of the arylene unit. Replacement of a phenylene with an oligophenylene unit produces a blue-shift in the emission, e. g. the poly(pentaphenylene vinylene) 58 is a blue emitter (2rnax = 446 nm) [71], while heterocydes induce red-shifts. This is particularly marked in the case of thiophene so that the polymer 59 actually emits in the near-infrared (7m lx = 740 nm) [72]. The picture with fused polycyclic aromatics is more complicated with the 1,4-naphthalene 19 [73] and 9,10-anthracene 60 [74] polymers both being markedly red-shifted in emission compared with PPV (1), while the 2,6-napthalene 18 [75] and 3,6-phenanthrene 61 [58] materials are slightly blue-shifted. 

The high reactivity of ortho-benzyne is also evident in 1,3-dipolar cycloadditions. The reaction is an extremely useful route to benzo-fused five-membered ring heterocydes. For example, azides give benzotriazoles, diazo compounds give (after... 

Abstract 2-pyridones are important heterocydes with great applicability in medicinal chemistry and this core structure can be found in compounds with various biological/medicinal applications. Here we show how microwave-assisted chemistry can be used to effectively synthesize and functionalize substituted monocydic 2-pyridones, 2-quinolones and other ring-fused 2-pyridones. The chapter covers recent advancements in this field mainly describing methods developed with instruments specially designed for microwave-assisted organic synthesis (MAOS). 

Chapman et al. (1974) found that protonated heterocydes including benzthiazolium bromide (102), possessing an alkyl substituent (e.g. benzyl) on the carbon adjacent to the positive nitrogen reacted with methylvinylketone to form adduct (103) which can be converted into fused pyridinium salts (104,105) (Scheme-29) (Chapanan et al. 1974). 

W.S. Hamama, Pyrazolones as versatile precursors for thesynthesisof fused and binary heterocydes, Synth. Commun. 31 (2001) 1335-1345. 

Thiophens Fused to Five-membered Aromatic Heterocydic Rings... 

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