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2-Aminopyridines ring closures with

Urban et al. effected the ring closure of 2-aminopyridines and diethyl malo-nate in ethanolic sodium ethoxide. 2-Amino-4-chloropyridine and diethyl 2-methoxyethyl malonate gave only the noncyclized product (68), which was then transformed in a separate reaction with N,N -dicyclohexylcarbodiimide in dimethylformamide at room temperature to the pyrido[l,2-a]pyrimidine (69).112 Besides diethyl malonates, the active esters107 108 1 13 117 and malonyl dichlorides52,118119 have also been used as reaction partners of 2-aminopyridines. [Pg.262]

By ring closure of the acrylates (73), 3-substitu ted 4-oxo-4//-py rido [ 1,2-a] -pyrimidines with chloroacetyl, 2-ethoxycarbonylvinyl, and nitro- and 4-chlorophenylsufonyl substituents have been prepared.22145-147 Reaction of 2-aminopyridine and the enamine (84) led to the 3-phenyl derivative (85), which is presumably formed by an addition-elimination mechanism.153... [Pg.268]

The almost exclusive ring closure at the a-position carries over to other electrophilic reactions of substituted 3 -aminopyridine derivatives. For example, the condensation of 3-aminopyridine with ethoxy-methylenemalonic ester (EMME) in dilute solution in boiling Dowtherm A gave the 1,5-naphthyridine 190.425,426 The only exception to date is that of 3-aminopyridine A -oxide which, as expected,... [Pg.337]

The aza-Wittig reaction of iminophosphoranes 60 with isocyanates affords the carbodiimides 61, which undergo ring closure to give 2-aminopyridine derivatives 62. ... [Pg.158]

Tetrazolo[l,5-a]pyridines have been prepared from either the corresponding halopyridine and sodium azide in the presence of acid with spontaneous electrocyclic ring closure, or by nitrosation of the appropriate 2-hydrazinopyridines (71T5121,76JOC1073) as shown in Scheme 70. The reaction of 2-nitroaminopyridines with hydrazine under the influence of Raney nickel (72JHC461) and 2-aminopyridines with p-toluenesulfonyl azide (79JHC1567) are two other useful routes to tetrazolo[l,5-a]pyridines. [Pg.901]

The reaction of 2potassium amide in liquid ammonia to give 2-cyanoimidazole, imidazole, and 2-aminopyridine has been investigated (911). It has been found that 2-chloropyrazine containing an excess of in position 1, on treatment with potassium amide in liquid ammonia at — 65° yields 2-aminopyrazine in which the exocyclic nitrogen contains all the excess and an addition-nucleophilic-ring opening-ring closure (ANRORC) mechanism was proposed (822). The mechanism of the conversions into imidazole (823) and... [Pg.125]

Ring-opening of the dichloride (50) with barium hydroxide, followed by ring-closure, gives 2-aminopyridine-3-carboxaldehyde (51) in 70% yield (Scheme 22). ... [Pg.232]

Another route was needed for the preparation of alkyl and alkoxy substituted analogs in die pyrrolo[2,3- ]pyiidine series. An attractive route was utilization of the highly function ized hetero[23- lpyndine intermediate available fiom the Dieckmann condensation of a diester intermediate0. The p> dine tetraesters 12 required by diis route were readily prepared in three steps. Mchael addition of 8 to 9 followed by intramolecular ring closure afforded pyridine 10, which was converted to the 6-chloropyridine 11 by phosphorous oxychloride. Treatment of the 6-chloropyridine triester 11 with sarcosine and sarcosine esters at room temperature afforded a series of 6-aminopyridines 12a-c. [Pg.135]

The [l,2,4]triazolo[l,5- ]pyridine system is usually constructed by the closure of the triazole ring either by oxidative formation of the NN bond or by condensation of the N-aminopyridine derivatives . Various compounds 78 were obtained by the oxidation of the amidine 77 with Mn02 (Scheme 47) <2003IJB2901, 2005ARK(xiii)21>. A dehydrative cyclization by treatment of formamidoximes 79 with trifluoroacetic anhydride (TFAA) has been used in the synthesis of 80 (Scheme 48), which are key building blocks in the preparation of DPP (IV) inhibitors <2005EJ03761, 2006JME3614>. [Pg.901]


See other pages where 2-Aminopyridines ring closures with is mentioned: [Pg.236]    [Pg.883]    [Pg.883]    [Pg.131]    [Pg.404]    [Pg.466]    [Pg.219]    [Pg.544]    [Pg.131]    [Pg.636]    [Pg.884]    [Pg.131]    [Pg.636]    [Pg.884]    [Pg.205]    [Pg.75]    [Pg.269]    [Pg.106]    [Pg.110]    [Pg.238]    [Pg.622]   
See also in sourсe #XX -- [ Pg.8 , Pg.8 , Pg.11 , Pg.11 , Pg.14 , Pg.14 , Pg.49 , Pg.432 , Pg.432 , Pg.494 , Pg.506 , Pg.506 ]




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2-Aminopyridine

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