Fert-Amine catalysts

As was the case with ligand 4,2-biphenyldi-fert-butylphosphine (6) effects the amination of acyclic secondary amines at room temperature [42 a, 48]. The catalyst derived from this commercially available ligand and Pd2(dba)3 promotes the coupling of 4-bromo-ferf-butylbenzene and di- -butylamine or AT-methylaniline in excellent yields at room temperature, Eq. (28). 

Just recently, Stauffer and Steinbeiser [96] have presented an intermole-cular consecutive aryl amination-Suzuki coupling sequence where, in the presence of potassium orthophosphate as a weak base and Pd[P(fert.-Bu)3]2 as a catalyst system, the morpholino-biaryl derivative 111 was obtained in moderate yield (Scheme 40). 

There is direct evidence, from ir and nmr spectra, that the fert-butyl cation is quantitatively formed when ferf-butyl chloride reacts with AICI3 in anhydrous liquid HCl. In the case of alkenes, Markovnikov s rule (p. 1019) is followed. Carbocation formation is particularly easy from some reagents, because of the stability of the cations. Triphenylmethyl chloride and 1-chloroadamantane alkylate activated aromatic rings (e.g., phenols, amines) with no catalyst or solvent. Ions as stable as this are less reactive than other carbocations and often attack only active substrates. The tropylium ion, for example, alkylates anisole, but not benzene. It was noted on p. 476 that relatively stable vinylic cations can be generated from certain vinylic compounds. These have been used to introduce vinylic groups into aryl substrates. Lewis acids, such as BF3 or AIEta, can also be used to alkylation of aromatic rings with alkene units. 

Bohn s VO(acac)2/chiral Schiff base oxidation system was recently adapted by Ellman in the large-scale synthesis of a-branched amines [47]. Here, fert-butyl disulfide 26 was oxidized to the corresponding thiosulfinate 27 employing hg-and 23b. The oxidation was carried out using as httle as 1 mol % of catalyst giving fert-butyl ferf-butanethiosulfinate (27) with 91% ee (Eq.3). Further transformations of the thiosulfinate led to optically active amines in high yields. 

Felthouse and Mills (321) report the amination of methyl ferf-butyl ether (MTBE) and isobutene to fert-butylamine using alumino- and borosilicate pentasil molecular sieve catalysts. The ether and alkene amination reactions were found to proceed preferentially under SCF conditions at temperatures on the order of 330°C and pressures greater than 193 bar. The smdy showed that MTBE can be used as a substitute raw material for terf-butylamine manufacture, but MTBE decomposition products of isobutene, methanol, and methanol conversion products are produced that require a more complicated product separation process than with isobutene as the only C4 substrate. 

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