Irradiation nonconventional

Microwave (MW) irradiation as a nonconventional reaction condition [703] has been applied in various areas of chemistry and technology to produce or destroy diverse materials and chemical compounds, as well as to accelerate chemical processes. The advantages of its use are the following [704] ... 

The use of microwave irradiation (MWI) as a nonconventional source of energy, a consequence of converting electromagnetic energy, had become very attractive for its applications to chemistry and material processing. In organic synthesis, the potential... 

Du XW, Jin Y, Zhao NQ, Fu YS, Kulinich SA (2008) Controlling surface states and photoluminescence of porous silicon by low-energy-ion irradiation. Appl Surf Sci 254(8) 2479-2482 El Houichet H, Oueslati M, Bessais B, Ezzaouia H (1997) Photoluminescence enhancement and degradation in porous silicon evidence for nonconventional photoinduced defects. J Lumin... 

A convenient and clean water-mediated synthesis of a series of 4-amino-2-ar-yl-1,2-dihydro pyrimido[l,2-a]benzimidazoles has been reported using alternative nonconventional energy sources [37]. The products were obtained in shorter times with excellent yields (78-89 %) from the multicomponent reaction of 2-ami-nobenzimidazole, malononitrile/ethylcyanoacetate, and carbonyl compounds (Scheme 8.26). The procedure does not involve the use of aity additional reagent/ catalyst, produces no waste, and represents a green synthetic protocol with high atom economy. The combination of microwave irradiation, ultrasonic irradiation, and aqueous-mediated conditions using multicomponent reactions leads to enhanced reaction rates, higher yields of pure products, easier workup, and sometimes selective conversions. Consequently, this protocol should be welcome in these environmentally aware days. 

The application of "on-water" organic chemistry in the synthesis of aza-heterocyclic compounds has seen a fremendous development in recent years. Water is xmdoubtedly the cheapest, most abundant, and environmentally benign solvent. The development of nonconventional techniques such as microwave irradiation and ultrasonification, and several novel catalysts have further aided to the aspect of green solvent system... 

Shelke et al. [80] S5mthesized various fluorine-containing compounds by conventional and nonconventional procedures by ultrasonication and microwave techniques. Various 3-substituted-l-phenyl-lH-pyrazole-4-carbaldehydes were treated with 3-(trifluoromethyl)-l-phenyl-lH-pyrazol-5(4H)-one (83) to give 4-((3-(4-aryl)-l-phenyl-lH-pyrazol-4-yl) methylene)-3-(trifluoromethyl)-l-phenyl-lH-pyrazol-5(4H)-one (85). Equivalent mole of 3-formylchromone and 3-(trifluoromethyl)-l-phenyl-lH-pyrazol-5(4H)-one by conventional method and nonconventional methods gave 3-(trifluoromethyl)-4-(4-oxo-4H chromon-3-yl)-methylene-l-phenyl-lH-pyrazol-(4H)-one (84) (Scheme 21). Compounds 84 and 85 were obtained in slightly better yields within 5-10 min under ultrasonication than in 2-3 min with microwave irradiation. 

Nanoscopic, partly hydroxylated magnesium fluorides (Mgp2 ,(0H), with x < 0.1) seem to possess appropriate characteristics for this synthesis [147]. Moreover, to further optimize the reaction conditions nonconventional methods to activate reactant molecules such as micro-waves or ultrasound irradiation were used. 

Apart from aminolysis and olefin metathesis the photoactivation of aminocar-bene complexes offers another nonconventional entry into peptide synthesis. Irradiation into the hypsochromic MLCT-band of chromium aminocarbenes such as 201 generates a ketene-like intermediate 204 that is trapped by amino acid esters such as 202 or 205 to produce dipeptides 203 or 206 after enantioselective protonation (Scheme 11.49) [106]. This photochemical protocol generally combines good yields with high diastereoselectivities and is especially attractive for the incorporation of a-alkyl a-amino acid esters into peptides that may be hampered in conventional peptide synthesis methodologies due to steric hindrance [106c]. 

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