Amines chloride-catalyzed

The reaction of higher alkyl chlorides with tin metal at 235°C is not practical because of the thermal decomposition which occurs before the products can be removed from the reaction zone. The reaction temperature necessary for the formation of dimethyl tin dichloride can be lowered considerably by the use of certain catalysts. Quaternary ammonium and phosphonium iodides allow the reaction to proceed in good yield at 150—160°C (109). An improvement in the process involves the use of amine—stannic chloride complexes or mixtures of stannic chloride and a quaternary ammonium or phosphonium compound (110). Use of these catalysts is claimed to yield dimethyl tin dichloride containing less than 0.1 wt % trimethyl tin chloride. Catalyzed direct reactions under pressure are used commercially to manufacture dimethyl tin dichloride. 

A practical synthesis of 2-arylamino-6-alkylaminopurines from 2,6-dichloropurine by base-assisted substitution of the 6-chloro substituent with cyclobutylamine followed by a new trimethylsilyl chloride-catalyzed displacement of the 2-chloro group in the intermediate purine with an aromatic amine has been published <06OPRD799>. 

Wright illustrated the effectiveness of chloride-catalyzed nitration for a number of amines of different basicity. Wright showed that weakly basic amines like iminodiacetonitrile and its dimethyl and tetramethyl derivatives are all nitrated in high yield with nitric acid-acetic anhydride mixtures in the absence of chloride ion. In contrast, the slightly more basic 3,3 -iminodipropionitrile is not appreciably nitrated with acetic anhydride-nitric acid, but the inclusion of a catalytic amount of the hydrochloride salt of the amine base generates the corresponding nitramine in 71 % yield. ... 

The founder of the chloride-catalyzed nitration of amines, G. F. Wright, has extensively reviewed chloride-catalyzed nitration. " Even 50 years later, the importance and success of this method as a route to nitramines is illustrated by the number of examples which can be found in the literature. 

Acetic anhydride-nitric acid mixtures are extensively used for chloride-catalyzed nitrations. Other nitrating agents have been used and involve similar sources of electropositive chlorine for intermediate chloramine formation. 4,10-Dinitro-4,10-diaza-2,6,8,12-tetraoxaisowurtzitane (TEX) (40), an insensitive high performance explosive (VOD 8665 m/s, d = 1.99 g/cm ), is synthesized by treating the dihydrochloride salt of the corresponding amine (39) with strong mixed acid. ... 

The role of dialkylchloramines as intermediates in the chloride-catalyzed nitration of secondary amines is discussed in Section 5.3.1. Wright and co-workers" studied this reaction further and prepared a number of dialkylchloramines by treating secondary amines with aqueous hypochlorous acid (Equation 5.12). Treatment of these dialkylchloramines with nitric acid in acetic anhydride forms the corresponding secondary nitramine, a result consistent with the chloride-catalyzed nitration of amines." ... 

In view of the highly carcinogenic nature of many nitrosamines any experiments involving their isolation must be discouraged, and for this reason, this section has only been written for completeness. This high toxicity is unfortunate because the preparation of nitrosamines from the parent amines is often facile and they provide a route to highly pure nitramines. Other equally useful methods for the synthesis of nitramines, such as the chloride-catalyzed nitration of secondary amines, also suffer from the formation of nitrosamines in appreciable amounts and must also be viewed with caution. 

Bismuth(lll) chloride catalyzes the intramolecular hetero-Diels-Alder reaction of aldimines, generated in situ from aromatic amines and the A -allyl derivative of o-aminobenzaldehyde, in acetonitrile at reflux to generate [l,6]naphthyridine derivatives <2002TL1573>. The hetero-Diels-Alder reaction of 3-aryl-2-benzoyl-2-propeneni-triles and enol ethers yields 2-alkoxy, 6-diaryl-3,4-dihydro-2//-pyran-5-carbonitriles (Scheme 29) <1997M1157>. 

Palladium catalysts that are free of halide ions effect the dimerization and carboxylation of butadiene to yield 3,8-nonadienoate esters. Palladium acetate, solubilized by a tertiary amine or an aromatic amine, gives the best yields and selectivities (equation 57).87 Palladium chloride catalyzes the hydrocarboxylation to yield primarily 3-pentenoates.88 The hydrocarboxylation of isoprene and chloroprene is regio-selective, placing the carboxy function at the least-hindered carbon (82% and 71% selectively) minor amounts of other products are obtained (equation 58). Cyclic dienes such as 1,3-cyclohexadiene and 1,3-cyclooctadiene are similarly hydrocarboxylated. 

Scheme 10. Two concurrent mechanisms for the amination of aryl chlorides catalyzed by P(tBu)3 complexes of palladium.

In a similar manner, treatment with an N,N-dialkylformamide leads to tertiary amines moreover, magnesium chloride, or better still calcium chloride, catalyzes the reaction. Other factors have been studied. ... 

The method is apparently limited to the preparation of certain aryl and high-molecular-weight ketoketenes, which are relatively resistant to dimerization. Thus, the dehydrohalogenation of a low-molecular-weight acyl chloride such as isobutyryl chloride gives dimethyl ketene dimer (60%). It is quite possible that the tertiary amine salt catalyzes the dimerization. ... 

Amination. The conversion of aryl chlorides to amines is catalyzed by Ni(OAc)2-2,2-bipyridine and sodium t-amylate/NaOH in THF. 

Hartwig was able to show that LiHMDS could serve as both an ammonia equivalent and as the stoichiometric base for the amination reaction catalyzed by Pd(f-Bu)3P.94 The reaction conditions tolerate many aryl bromides and chlorides, but due to the size of LiHMDS, or/Ao-substituted haloarenes are not acceptable. As before, acidic workup reveals the aniline by cleavage of the N-Si bond. 

The efficient synthesis of aminoindolizines 53 was successfully achieved in PEG using copper(I) chloride catalyzed three-component reaction of pyridine- or quinolin-2-carboxaldehyde with terminal alkynes and secondary amines (Scheme 30) [54]. The reaction in conventional solvents gave lower yields of the product 53. The structure of the obtained aminoindolizines was confirmed by the X-ray crystallography data (53, R =4-MeC6H4, r2]sjr3=morpholino). 

Indium(III) chloride catalyzes the microwave-assisted reaction of a-azidochalcones 34 with 1,3-dicarbonyl compounds 35 in water to form polysubstituted pyrroles 36 (Scheme 11) [42]. The reaction has been explained through the formation of an azirine interm iate. Addition of enols from 1,3-dicarbonyl compounds on azirines forms aziridines, which undergo ring opening to form a,(5-unsaturated amines. The amines cyclize via dihydropyrroles to form pyrroles. 

Disubstituted indoles are obtained by iron(II) chloride-catalyzed ring opening of 3-phenyl-2//-azirines and amination of an aromatic C-H bond (Scheme 4-354). Moderate to good yields are achieved by this method, which tolerates a number of functional groups like bromine, fluorine, nitro, methoxy, trifuoromethyl, tert-butyldimethylsilyloxy, alkenyl, and pivaloyl substituents. ... 

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