2- aminopyridines, phosphorus

Bromopyridine has been made by direct bromination of pyridine - from N-methyl-2-pyridone with phosphorus penta-bromide and phosphorus oxybromide from 2-aminopyridine by diazotization with amyl nitrite in 20% hydrobromic acid from sodium 2-pyridinediazotate by solution in concentrated hydrobromic acid and from 2-aminopyridinc by diazotization in the presence of bromine and concentrated hydrobromic acidd The method described here is essentially that of Craig. 

Studies on the synthesis of [l,2,4,3]triazaphospholo[l,5-tf]pyridines have been reported by Schmidpeter et al. <1993JPR458, 1994PS381, 1995ZNB558>. The reaction pathway starts from 2-aminopyridine 147 which is first subjected to an Anamination reaction to give 1,2-diaminopyridinium iodide 148, and this compound is treated with tris-dimethylaminophosphine to yield the five-membered phosphorus-containing heterocycle 149. 

Only resinous products and methyl 6-acetamidopyridine-3-carboxylate were obtained when methyl 6-aminopyridine-3-carboxylate was reacted with ethyl 2-acetoxyacetoacetate by heating in phosphorus pentoxide, methanesulfonic acid, or polyphosphoric acid in the absence or presence of a solvent such as toluene, xylene, or methylene chloride. However the desired methyl 3-acetoxy-2-methyl-4-oxo-4//-pyrido[ 1,2-a]pyrimidine-7-carboxylate 93 was obtained when the above components were reacted in N, A-dimethylacetamide in the presence of polyphosphoric acid at 100°C for 48 hours (84FES837). 

The use of polyphosphoric acid as a reagent for the synthesis of 2-substituted oxazolo[4,5-6]pyridines (449) has been reported (Scheme 52) (89JHC289, 90JHC1825). For example, acylating 2-chloro-3-aminopyridine (447) with m- or p-nitrobenzoyl chloride followed by heating of the intermediate (448) in polyphosphoric acid (85% phosphorus pentoxide) for 3 h at 200°C gave good yields of the oxazolopyridines (449). 

We are investigating a series of reactions of aminopyridines and aminopyrimidines and main group compounds. These heterocycles can form adducts with both kinds of nitrogen atoms pyridinic or anilinic. Bonding of several aminopyridines to heteroatoms such as boron, silicon, or phosphorus gives polyfunctional molecules rich in lone pairs and therefore candidates to be used as ligands. 

A similar reaction performed with P(NMe2)3 and 2-aminopyridine gives trisaminophosphorus compound. Borane addition gives the corresponding phosphorus and pyridinic adducts (Figure 15). 

The reaction of 2-aminopyridine (28) with sodium nitrite, bromine, and HBr gives 2-bromopyridine (70) in 87% yield (34JA23I 5IJA4773). Bromine has also been introduced into quinolines by treating 2- or 4-methoxyquinolines with phosphorus tribromide in DMF to furnish 2-bromo- or 4-bromoquinoline in 78% and 68% yields, respectively... 

In a search for tervalent phosphorus acid derivatives with better phosphitylation properties than usual aminophosphines or phosphoramidites Nifant ev et al. have prepared several new reagents. These include pyrazole derivatives, e.g. (51), 2-aminopyridine derivatives, e.g. (52), amidine derivatives, e.g. (53), and hydrazine derivatives, e.g. (54). They were prepared by standard methods and examined for their reactivity towards alcohols and, in the case of the amidine derivatives, for their tendency to isomerize by migration of the phosphorus group to the other nitrogen atom. Another type of reactive tervalent phosphorus acid derivative is phosphites derived from hydroxylamine. Several stable derivatives, e.g. (55) and (56), have been prepared and substitution reactions with alcohols studied. ... 

The thermionic detector was used [26] in phosphorus mode for the capillary SFC analysis of thiophosphinic esters derived from steroids by reaction with dimcAhyl-thiophosphinic chloride in the presence of 4-dimethyl-aminopyridine catalyst. 

Aminopyridine condenses with cinnamaldehyde in the presence of anhydrous zinc chloride to give a product that, on treatment with sodium borohydride, gives 2-cinnamylaminopyridine similarly, various 2-(substituted-cinnamyl)aminopyridines are prepared from 2-aminopyridine and substituted cinnamaldehydes. When 2-aminopyiidine and formylferrocene are boiled under reflux in toluene containing phosphorus oxychloride, there is isolated a product which, when reduced with sodium borohydride, gives 2-pyridylamino-methyl ferrocene. ... 

Schemes 58-62. A new non-rigid phosphine ligand was synthesized and reacted with Fe(CO)5 to form the mononuclear iron complex (Equation (81)). Phosphino-oxazoline ligands were used as assembling ligands for hetero-metallic complexes, where the phosphorus atom binds to iron and the nitrogen atoms act as donor atoms to copper, cobalt, or palladium (Scheme 58). The copper complex catalyzes cyclopropanation and Diels-Alder reactions. When 2-(A -diphenylphosphinomethyl-A -cyclohexyl)aminopyridine (NNP) reacts with Fe(CO)5 in ethanol, /ra .r-(OC)3Fe(NNP)2 is formed (Scheme 59). This monometallic complex can then be reacted with a copper salt in CH2GI2 to form a complex having an Fe-Cu dative bond. The complex was demonstrated to be an efficient catalyst for the cyclopropanation of styrene by ethyl diazoacetate and for the Diels-Alder reaction of cyclopentadiene and methacrolein. No other heterometallic complexes have been shown to have such reactivity. Previously known...

Aminopyridine is converted by phosphorus trichloride into di-(4-pyridyl) amine ss. 

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