Carbaldehydes pyridine-2-carbaldehyde

In at least one case, the standard Bucherer-Bergs conditions gave rise to oxazole rather hydantoin. Specifically, when 5-benzyloxy-pyridine-2-carbaldehyde (11) was treated with potassium cyanide, ammonium chloride, and ammonium carbonate in boiling ethanol/water, 5-amino-oxazol-2-ol 12 was obtained. Subsequent heating of oxazole 12 with acetic acid at reflux overnight then produced the Bucherer-Bergs product, hydantoin 13. ... 

An interesting intermediate 30 was proposed to result from the sequential addition of pyridine to tetrachlorocyclopropene (31). Compound 30 represents an alkyl nitrogen ylide with two 1-chloroalkyl pyridinium moieties in the same molecule. Pyridines with electron-withdrawing groups and heterocycles with an electron-deficient nitrogen, for example, pyridine-3-carbaldehyde or quinoline, react with 31 to yield the corresponding mono-substituted products 32a and 32b (83JOC2629) (Scheme 8). 

Ligand abbreviations bi = 2,2 -bi-2-imidazoline bt = 2,2 -bi-2-thiazoline bpy = 2,2 -bipyridine phen = 1,10-phenanthroline phy = l,10-phenanthroline-2-carbaldehyde phenylhydrazone bpp = 2,6-bis(pyrazol-3-yl)pyridine paptH = 2-(2-pyridylamino)-4-(2-pyridyl)thiazole 2-pic = 2-picolylamine L = macrocyclic ligand derived from condensation of 2,6-diacetylpyridine with 3,6-dioxaoctane-1,8-diamine Hjthpu = pyruvic acid thiosemicarbazone Hjthpx = pyridoxal thiosemicarbazone salen = dianion of W,iV -ethylenebis(salicylideneimine) H2fsa2en = dianion of fV,JV -ethylenebis(3-carboxysalicylaldimine). 

Chelating aldehydes such as 2-pyridine carbaldehyde and 2-dimethylamino benzaldehyde improve the stability of the aldehyde complexes via N,0 chelation. NMR studies show that the complexes are present in solution without an excess of aldehyde and can be formed in the presence of donor ligands. The X-ray structures showed longer and weaker Zn—O bonds when more than one chelating ligand was present. IR demonstrates the variation in C=0 bond strengths and how the environment of the zinc ion will influence potential catalytic activity via reaction rates or pathways. Tetrahedral chelate complexes, and octahedral bis- and tris-chelate complexes, were isolated.843... 

With the aid of a Knoevenagel condensation and a Staudinger reaction, 2-azidocyclopent-l-ene 1-carbaldehydes (195) can be converted into suitable products for a cyclopenta[b]pyridine synthesis [89JCS(P1)1369], as shown in Scheme 72. In order to bring the ester carbonyl function and the imino-phosphorane group into close proximity suitable for cyclization reactions, the 1,3-diene system 196 should possess the s-cis conformation. Furthermore, the exocyclic double bond should show a cis conformation. To achieve... 

An Ru—Mn bond is present in the complexes [(CO)5MnRu(Me)(CO)2L] where L is N,N -diisopropyl-1,4-diaza-1,3-butadiene, or pyridine-2-carbaldehyde-A-isopropylimine crystallographic... 

Cholinesterase inhibition, the mechanism whereby a number of insecticides and nerve gases function, may be reversed by acid salts of pyridine-2-carbaldehyde oxime (51). The chloride (61JPS109, 64USP3155674), iodide (57USP2816113) and methanesulfonate... 

Chloro-2-aryl-2//-chromene-3-carbaldehydes, formed from the reaction of flav-4-ones with dimethylformamide (DMF)/POCl3, react with ethyl 3-aminocrotonate under Hantzsch conditions to give ethyl 2-methyl-5-aryl-5H-chromen[3,4-f]pyridine carboxylates in good yields <2001SC2589>. 

In contrast to wild-type BFD, BAL accepts aromatic aldehydes substituted in the ortho position as well. Only a few aromatic aldehydes, such as pyridine 3- and 4-carbaldehyde as well as sterically exceedingly demanding aldehydes, resulted either in very low yields or in no benzoin condensation at all [62]. Moreover, mono- and dimethoxyacetaldehyde are good substrates for BAL, leading to highly functionalized enantiopure hydroxypropiophenone derivatives (Scheme 2.2.7.22) [63]. 

Occasionally, [2.2.3]cyclazines have been obtained from pyridines in reasonable yields. Thus (251) is formed in a reaction of the 2-vinylpyridine (252) with methyl propiolate <71 JCS(C)3296>. Acylative cyclization of pyridine-2-carbaldehyde with a,/3-unsaturated carbonyl compounds provides a convenient route to l-acyl[2.2.3]cyclazines (Scheme 38) <74H(2)585). 

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