Amines, arylation with

Photolysis of aryl azides in amine solution, with a tertiary amine as cosolvent to promote stabilization of the singlet nitrene, has met with some success. For example, the yield of 2-piperidino-3 W-azepme. obtained by the photolysis of phenyl azide in piperidine, is increased from 35 to 58% in the presence of A A /V. /V -tetramethylethylenediamine (TMLDA).180 Also, an improved yield (36 to 60 %) of A,(V-diethyl-3W-azepin-2-amine (38, R = Et) can be obtained by irradiating phenyl azide in triethylamine, rather than in dicthylaminc, solution.181 Photolysis (or thermolysis) of phenyl azide in TMEDA produces, in each case, 38 (R = Et) in 40% yield.181 In contrast, irradiation of phenyl azide in aniline with trimethylamine as cosolvent furnishes jV-phenyl-377-azepin-2-amine (32, R = Ph) in only low yield (2%).35... 

Doyle et al. (1977 c) and Oae et al. (1980) reported modified Meerwein arylations with significant improvements in the yield by the use of aryl amines and alkyl nitrites in place of arenediazonium salts. However, good yields are only achieved if alkenes activated by electron-withdrawing groups are present. 

The equation for a net chemical reaction represents the overall transformation of reactants into products. Thus, thallium Ill) ions oxidize iron(II) ions according to Eq. (1-1), and a secondary amine reacts with an aryl chloride as in Eq. (1-2). 

Aryl-substituted 6-methyl-4//-pyrazolo[3,4-c]-l,2,5-oxadiazoles 275 are easily obtained in 88-97% yields by the oxidation of 2-aryl-5-methyl-4-nitroso-2//-pyrazol-3-amines 274 with Pb(OAc)4 (Equation 52) <2000S72>. 

Only a few more recent examples of the numerous studies on N-arylations with aryllead triacetates will be discussed here. For earlier publications in this field, the interested reader is referred to the pioneering arylations of aliphatic and aromatic amines by Barton s group, 8 as well as the comprehensive review article by Elliott and... 

The silylated tin compound 199, obtained from tributyltin hydride and N-bis(trimethylsilyl)propargylamine (198) in the presence of a trace of AIBN (2,2/-azobisisobutyronitrile), is a versatile reagent for the preparation of allylic amines. Treatment with aryl bromides ArBr (Ar = Ph, 4-MeOCgH4, 4-O2NC6H4 etc.) under Pd(PPh3)4 catalysis yields the silylated amines 200, which are hydrolysed by acids to the free amines 201. 199 is converted into the lithium compound 202, which is transformed into 203 by aqueous ammonium chloride and into 204 by the action of alkyl halides RX (R = Me, Et or allyl) (equation 76)204. 

S-Protonated Aryliminium Salts Hesse has made a much more extensive study of the reaction of aryl primary amines (58) with higher aldehydes (see 59) and a suitable alkene, usually styrene or a-methylstyrene, and found that high yields of tetra-hydroisoquinoline (60) could be obtained even when an electron-withdrawing group was present in the aryl ring. Carbonium ion (61) appeared likely as an intermediate. 

More recently, Polish chemists have reported a synthesis of both aryl and aliphatic secondary nitramines by treating amine substrates with ethyl magnesium bromide followed by reaction with n-butyl nitrate (Equation 5.8). This method, which uses nonpolar solvents like hexane or benzene, has been used to synthesize aliphatic secondary nitramines, and At-nitro-A-methylanilines which otherwise undergo facile Bamberger rearrangement in the presence of acid. The direct nitration of At-unsubstituted arylamines usually requires the presence of an electron-withdrawing group. Reactions are retarded and yields are low for sterically hindered amines. 

Nagao has disclosed bifunctional chiral sulfonamide 69 as being effective for the thiolytic ASD of meso-cyclic anhydrides in up to 98% ee when employed at the 5 mol% level for 20 h at room temperature in ether [228], Catalyst 69 is a 1,2-diamine derivative in which one of the nitrogens presents as an acidic NH group (part of an electron deficient aryl sulfonamide) and the other as a nucleophihc/basic teri-amine group with the intention to act synergistically in activation of the substrate carbonyl function and thiol nucleophile respectively (Fig. 16) [228],... 

Fagnou et al. reported the synthesis of mukonine (11) starting from methyl vanillate (644). This synthesis uses both a palladium(0)-catalyzed intermolecular direct arylation and an intramolecular cyclization reaction. Triflation of methyl vanillate (644) afforded the aryl triflate 645. Using a Buchwald-Flartwig amination protocol, the latter was subjected to direct arylation with 2-chloroaniline (646) to furnish the corresponding diarylamine 647. Finally, intramolecular cyclization of 647 afforded mukonine (11). To date, this is the best synthesis (three steps, 75% overall yield) available for mukonine based on commercially available methyl vanillate (644) (582) (Scheme 5.45). 

Substituted 6-iodopyridazines were the first representatives studied <1995JOC748>. Interestingly, a free amino group is well tolerated and a comparison of Stille reactions on 6-iodo- 170 and 6-chloropyridazin-3-amine 171 with aryl(tributyl)stannanes remarkably revealed that the latter react substantially faster (Equation 28 and Table 7) <2000T1777>. 

Aryl amines react with an excess of an endocyclic ene-carbamate, including tert- mVf 1,2,3,4-tetrahydro-l-pyridi-necarboxylate, on the surface of Montmorillonite KSF clay to give 4-aminobutyloctahydrobenzo[ ][l,6]naphthyr-idines in excellent yields and moderate diastereoselectivity <2004TL7947>. 

The bromoaldehyde (182) reacts with primary amines to give the pyrrolo[3,4-treatment with hydrazine hydrate is converted into (183 R = NH2) (78S463). The acetonylpyrimidines (184) react with ammonia and primary amines to give pyr-rolopyrimidines, e.g. (185). Nucleophilic displacement of the halogen is probably effected... 

Ramjeesingh and Kahlenberg38 reported the synthesis of 6-deoxy-6-isothiocyanato-D-glucopyranose (24). They employed the common method of synthesis of aryl isothiocyanates by treatment of amine 22 with carbon disulfide in the presence of dicyclohexylcarbodiimide (DCC). 

There are seemingly many different ways in which amines can be prepared. However, a careful look at these methods reveals that they fall into three main groups of reactions. The first group starts with a simple amine, or with ammonia, and builds up the carbon framework by alkylation or arylation reactions on nitrogen, as discussed in Section 23-9D ... 

Thiazines such as 50 have been prepared by the reaction of C1CH2-CR1=CR2NCS (R1 = alkyl, cycloalkyl, aryl) with a secondary amine in an organic solvent (Scheme 30) (77EGP128124). 

A highly regioselective amination of 6-aryl-2,4-dichloropyrimidines has been developed using palladium catalysis. The reaction which works well with secondary aliphatic amines and with anilines gives the 4-substituted products.46 Palladium catalysis has also been used in the regioselective coupling of 2,3-dibromopyridine with a series... 

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