Heterocycles catalytic synthesis

Catalytic synthesis of natural fused O- and N-heterocycles 98JHC1057. 

Due to its marked atom economy, the intramolecular hydroamination of alkenes represents an attractive process for the catalytic synthesis of nitrogen-containing organic compounds. Moreover, the nitrogen heterocycles obtained by hydroamination/cyclisation processes are frequently found in numerous pharmacologically active products. The pioneering work in this area was reported by Marks et al. who have used lanthanocenes to perform hydroamination/cyclisation reactions in 1992. These reactions can be performed in an intermolecular fashion and transition metals are by far the more efficient catalysts for promotion of these transformations via activation of the... 

An advantage of the metal-catalyzed conversion of styrenyl ethers to chromenes is that control of relative stereochemistry on the carbocyclic substrate before catalytic synthesis of chromenes can lead to the formation of various functionalized heterocycles that are diastereomerically pure (Table 1). 

He M, Bode JW (2005) Catalytic synthesis of y-lactams via direct annulations of enals and N-sulfonylimines. Qrg Lett 7 3131-3134 He M, Struble JR, Bode JW (2006) Highly enantioselective azadiene Diels-Alder reactions catalyzed by chiral N-heterocyclic carbenes. J Am Chem Soc 128 8418-8420... 

N-N Bond scission and synthesis of N-heterocycles 86UK1785. Carbodiimides, formation of N-heterocycles from 82UK848 81AG855. Catalytic synthesis of N-heterocycles 83KGS1587, 83YGK604. Condensed N-heterocycles, syntheses using modified Japp-Klingemann... 

Catalytic synthesis of heterocyclic compounds via formation of carbon—heteroatom bond using aryl and... 

Baker, M.V., Brown, D.H., Simpson, P.V. et al. (2006) Palladium, rhodium and platinum complexes of ortho-xy y - mk A bis-A-heterocyclic carbenes synthesis, structure and catalytic activity. J. Organomet. Chem., 691, 5845-55. 

Intramolecular addition of alcohols across alkenes was established as one of the first examples of this type, and represents a classic approach to the catalytic synthesis of oxygenated heterocycles [12]. A first reaction to this end was described in 1975, with the conversion of 2-allyl phenols 1 to their corresponding dihydrobenzofuranes 2. 

Andrson JD, Cottom HB, Larson SB, Nord LD, Revankar GR, Robins RK (1990) Synthesis of certain pyrazolo[3,4-Heterocycl Chem 27 439-453 Heravi MM, Motamedi R, Seifi N, Bamoharram FF (2006) Catalytic synthesis of 6-aryl-1/f-pyrazolo[3,4-d]pyrimidin-4[5//]-ones by heteropolyacid Hi fNaPjWjdOud] and HjPWijO, . J Mol Catal A Chem 249 1-3... 

Catalytic synthesis of natural fused O- and N-heterocycles 98JHC1057. Chemoenzymatic synthesis of chiral biologically active heterocycles 97F307. Combinatorial synthesis of multicomponerrt nrixtures, among them rrrixtures of heterocycles, for screening of bioactive compounds 99JMC3743. 

Synthesis of Heterocycles. Novel synthesis of 1,3-dioxolanes was suggested, which starts with the formation of an intermediate carbonyl ylide from dimethyl diazomalonate and a carbonyl compound (aldehyde or quinone) in the presence of catalytic amounts of Rh. Once formed, the ylide undergoes dipolar [3 + 2] cycloaddition with another equivalent of carbonyl compound to furnish a five-membered heterocycle (eqs 25 and 26). Employment of aldimines in this reaction allowed for preparation of 1,3-imidazolidines (eq 27) and 1,3-oxazolidines (eq 28). ... 

Prostakov NS (1976) Catalytic synthesis and transformations of heterocyclic compounds. 

Green Catalytic Synthesis of Heterocyclic Structures Using Carbon Dioxide and Related... 

North and coworkers recently described an efficient and wide-scope catalytic synthesis of both heterocycles of type A and C (Figure 17) by variation of the reaction temperature [138]. In an initial screening phase, a bimetallic Al(salen) complex was used as a Lewis acid activator in conjxmction with Bu4NBr as nucleophilic cocatalyst at 70 °C in a sealed tube using 2-7 equivalent of CS2 and propylene oxide as substrate. A reaction temperature of 50 °C was found to be optimal considering both the chemical yield of the process as well as the chemoselectivity for the l,3-oxathiolane-2-thione product (96%, ratio A/C 8.0) using only 1.8 equivalent of CS2-... 

Catalytic asymmetric synthesis with participation and formation of heterocycles (including asymmetric phase transfer reactions and asymmetric reactions with chiral Lewis catalysts) 93MI1. 

Allylic protection groups and their removal through catalytic palladium Tr-allyl methodology in synthesis of heterocycles 98T2967. 

Fewer procedures have been explored recently for the synthesis of simple six-membered heterocycles by microwave-assisted MCRs. Libraries of 3,5,6-trisubstituted 2-pyridones have been prepared by the rapid solution phase three-component condensation of CH-acidic carbonyl compounds 44, NJ -dimethylformamide dimethyl acetal 45 and methylene active nitriles 47 imder microwave irradiation [77]. In this one-pot, two-step process for the synthesis of simple pyridones, initial condensation between 44 and 45 under solvent-free conditions was facilitated in 5 -10 min at either ambient temperature or 100 ° C by microwave irradiation, depending upon the CH-acidic carbonyl compound 44 used, to give enamine intermediate 46 (Scheme 19). Addition of the nitrile 47 and catalytic piperidine, and irradiation at 100 °C for 5 min, gave a library of 2-pyridones 48 in reasonable overall yield and high individual purities. 

UV irradiation of heterocycles such as 53 in ethanol containing catalytic iodine leads to oxidative cyclization affording tosylphenanthrenoids 54 <96JOC1188>. The synthesis of a heterocycle related to 53 was accomplished by a titanium coupling reaction <96TL2721>. 

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