Al-Heterocyclics

Al-Heterocycles, formation from olefins and acetylenes in a metallocomplex-catalyzed cycloaddition reaction and further transformations 98IZV816. 

Hashigushi, S. et al. Heterocycles (HTCYAM) 24, 2273 (1986). further synthetic routes for carumonam and its intermediates ... 

The majority of Al-heterocyclic carbenes and their metal complexes are obtained from cyclic azolium derivatives (Fig. 8). Nevertheless, the first complex with a heteroatom stabilized carbene ligand, although it was not recognized as such, was prepared by Tschugajeff et al. as early as 1925 [157]. It was later identified as a heterocarbene complex [158], Tschugajeff reacted the nucleophihc proton base... 

Trochimowicz HJ, et al Heterocyclic and miscellaneous nitrogen compounds. In Clayton GD, Clayton EE (eds) Patty s Industrial Hygiene and Toxicology, 4th ed, Vol II, Part E, Toxicology, pp 3390-3394. New York, John Wiley and Sons, 1994... 

Synthesis of Heterocycles through Nitrenes T. Kametani et al., Heterocycles, 1974, 2, 209-226. 

Alkynes bearing an adjacent Al-heterocycle, such as 5-ethynyl-1 -methyl-imidazole and 1-propargylbenzotriazole, readily alkylate benzene in the presence of triflic acid to yield diphenyl-substituted products.308 Isomeric ethynylpyridines exhibit distinct differences in reactivity 3-ethynylpyridine exhibits the highest reactivity, whereas 2-ethynylpyridine is the least reactive [Eq. (5.116)]. This is consistent with the involvement of dicationic intermediates as the de facto alkylating agents. Indeed,... 

Butler, L. M., Sinha, R., et al. Heterocyclic amines, meat intake, and association with colon cancer in a population-based study. Am. J. Epidemiol. 157(5), 434 145, 2003. 

According to the procedure of Juaristi et al., heterocycle (S)-3 (5.0 g, 18.4 mmol), 40 mL of EtOAc, 0.5 g of 10% Pd(C), and 0.4 mL of acetic acid is placed in a hydrogenation flask. The reaction mixture is pressurized to 75 atm of hydrogen, heated to 45 °C, and stirred for 24 h. The catalyst is removed by filtration over Celite, the filtrate is washed with aqueous 10% NaHC03, dried over anhydrous Na2S04, filtered, and evaporated at reduced pressure to give 4.5 g (90%) of 1-benzoyl-2(S)-tert-butyl-3-methylperhydropyrimidin-4-one [(S(-4], mp... 

Oxidative insertion into the arylbromide, carbonylation, and nucleophilic attack on the carbonyl M. Mori et al Heterocycles, group with elimination of Pd(0) completes the catalytic cycle. No doubt the palladium has a 1979,12, 921. number (1-2) of phosphines complexed to it during the reaction and these keep the Pd(0) in solution between cycles. 

Robbana-Bamat, S. et al., Heterocyclic amines occurrence and prevention in cooked food, Environ. Health Perspect., 104, 280, 1996. 

In order to vary the electronic situation at the carbene carbon atom a number of carbo- and heterocycle-annulated imidazolin-2-ylidenes like the benzobis(imida-zolin-2-ylidenes) [58-60] and the singly or doubly pyrido-annulated Al-heterocyclic carbenes [61-63] have been prepared and studied. Additional carbenes derived from a five-membered heterocycle like triazolin-5-ylidenes 10 [36], which reveals properties similar to the imidazolin-2-ylidenes 5 and thiazolin-2-ylidene 11 [37] exhibiting characteristic properties comparable to the saturated imidazolidm-2ylidenes 7 have also been prepared. Bertrand reported the 1,2,4-triazolium dication 12 [64]. Although all attempts to isolate the free dicarbene species from this dication have failed so far, silver complexes [65] as well as homo- and heterobimetallic iridium and rhodium complexes of the triazolin-3,5-diylidene have been prepared [66]. The 1,2,4-triazolium salts and the thiazolium salts have been used successfully as precatalysts for inter- [67] and intramolecular benzoin condensations [68]. 

The early syntheses of this ring system, based on the Skraup reaction on 2-aminoanthraquinones, have been augmented by a pericyclic approach. The [4+2]-cycloaddition of dimetltylenecyclohexane to quinoline-5,8-quinones gives high yields of the adducts, which are readily oxidised to the tetralydronaphtho[2,3-g]-quinolines (N. Oda et al.. Heterocycles, 1981, 1, 857). 

Tetrahedron Letters, 1978, 2723), whereas onychine (103) from Onychopetalum amazonicum is based on a 2- benzoyl -pyridine sub-structure (J. Koyama et al.. Heterocycles, 1979, 12, 1017). 

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