Pyridine fused tricyclic

The ring closure of A/-ethyl-/V-(3,4-alkylenedioxyphenylamino)methy-lenemalonates (839) in polyphosphoric acid at 120-130°C for 30 min afforded linearly fused tricyclic pyridine-3-carboxylates (840) in over 90% yields (73JAP6479). 

We also discovered the ability of 2-azadienes of this sort to cycloadd to unactivated carbon—carbon double and triple bonds in an intramolecular fashion (89CC267) (Scheme 50) such a process appears to be one of the first examples of intramolecular [4 + 2] cycloadditions of simple 2-azadienes. Azadiene 216 was made from O-allyl salicylaldehyde 215 (R = allyl) and heated at 120°C in toluene to furnish the trans-fused tricyclic adduct 217 in excellent yield further dehydrogenation of 217 with DDQ afforded 5H-[ 1 ]-benzopyran[4,3-6]pyridine 218. On the other hand, when 0-(2-butynyl) salicylaldehyde 215 (R = 2-butynyl) was transformed into azadiene 219 and subjected to heating in a sealed tube at 150°C, pyridine 222 was isolated in very high yield. Its formation can be rationalized to occur via the expected Diels-Alder intermediate 220 thus, [1,5]-H shift in 220 would give rise to tautomer 221, which would suffer electro-cyclic ring-opening and aromatization to pyridine derivative 222. 

There exist many types of azoloquinolines, and therefore it is necessary to define the objects of interest to be described in this review. The tricyclic azoloquinolines reviewed in this article have an azole ring fused to the benzene ring of quinoline (not isoquinoline derivatives) in positions / g, and h. This means that the benzene ring is between azole and pyridine rings, and all of them are ortho-peri condensed. The azole and benzene rings do not have a common heteroatom, and also a carbon... 

The tetraaza-tricyclic compound 326 is the main product of the reaction of CS2 with the mono-protected triamino-pyridylhydrazine 325 <1990JME656> (Equation 56). The lactone 328, which is fused to a hexahydro(l,2,3-tri-azolo)[3,4-tf]pyridine, is formed by thermolysis of the azide 327 <1998TL4203> (Equation 57). 

A prototypical series of monocyclic and tricyclic agents with potency in the nalidixic acid - oxolinic acid range has been reported [89]. The enantiomers of the tricycle (55), which lacks the ring fused to the 5- and 6-positions of the pyridine portion common to most quinolones, have been evaluated in vitro, and... 

Acid treatment of (6) furnishes products (13) including minor quantities of tricyclic condensation products, which result from the reaction of (13) with excess (6). This side reaction may be extended to become a synthesis of double anellated pyridines when (6) is fused with cyclic 1,3-dicarbonyl compounds. As expected, the spatial requirement of the acyl substituent R affects the yield of (15) (87TH1). (See Fig. 7.) Dipyrrolo[3,4-b 3, 4 -e]-pyridinediones of type (15a) were synthesized by Snyder et al. starting... 

Van Emelen, K., De Wit, T., Hoornaert, G. J., Compernolle, F. Synthesis of cis-fused hexahydro-4aH-indeno[1,2-b]pyridines via intramolecular Ritter reaction and their conversion to tricyclic analogs of NK-1 and dopamine receptor ligands. Tetrahedron 2002, 58,4225-4236. 

C.-X. Yan, Z.-X. Sun, Y. Cheng, Synthesis 2012, 865-874. Construction of novel tricyclic fused-ring systems by the multicomponent reactions of imidazo[l,5-a]pyridine carbenes with aromatic ortho-dialdehydes and electron-deficient alkynes. 

Tricyclic fused 3-aminopyridines 93 could also be assembled via intramolecular CpCo(C2H4)2-catalyzed [2- -2-1-2] cycloaddition between ynamides, nitriles, and alkynes (Scheme 1.26) [47]. Of particular interest, one of the cycloadducts could be used in a rare type of silylated pyridine Hiyama cross-coupling to give 95 in 77 % yield. 

---