Methylenecyclopropanes hydroamination

Ruthenium complexes mediate the hydroamination of ethylene with pyridine.589 The reaction, however, is not catalytic, because of strong complexation of the amine to metal sites. Iridium complexes with chiral diphosphine ligands and a small amount of fluoride cocatalyst are effective in inducing asymmetric alkene hydroamination reaction of norbomene with aniline [the best enantiomeric excess (ee) values exceed 90%].590 Strained methylenecyclopropanes react with ring opening to yield isomeric allylic enamines 591... 

Cazes et al. reported the Pd-catalyzed intermolecular hydroamination of substituted allenes using aliphatic amines in the presence of triethylammonium iodide leading to allylic amines [19]. In a way similar to the Pd-catalyzed hydrocarbona-tion reactions we reported that the hydroamination of allenes [20], enynes [21], methylenecyclopropanes [22], and cyclopropene [10] proceeds most probably via oxidative addition of an N-H bond under neutral or acidic conditions to give allylic amines. The presence of benzoic acid as an additive promotes the Pd-medi-ated inter- and intramolecular hydroamination of internal alkynes [23]. Intramolecular hydroamination has attracted more attention in recent years, because of its importance in the synthesis of a variety of nitrogen-containing heterocycles found in many biologically important compounds. The metal-catalyzed intramolecular hydroamination/cyclization of aminoalkenes, aminodienes, aminoallenes, and aminoalkynes has been abundantly documented [23]. 

The intermolecular addition of carbamates to 1,3-dienes (equation 147) under mild conditions has been described as well. The hydrothiolation of 1,3-dienes has also been reported. " Other related conjugate additions can be performed over methylenecyclopropanes (equation 148) with sulfonamides and the resulting product cyclizes by a second hydroamination of an olefin, finally yielding cyclic sulfonamides. This behavior is reproduced in a similar reaction for the ring opening of vinylcyclopropanes with sulfonamides. One more example in this group of reactions is the synthesis of dUiydrobenzofurans from aryl-allyl ethers. ... 

Schafer found that the bulky bis(amidate) complex is an effective catalyst for intermolecular hydroamination of terminal alkyl alkynes with alkylamines, giving exclusively the anti-Markovnikov aldimine product [309]. The same titanium complexes can also be utilized in the hydroamination of substituted allenes in good yields (Scheme 14.132). Under the catalysis of an imidotitanium complex, the highly strained methylenecyclopropane can undergo hydroamination reaction with either aromatic or aliphatic amines, to give ring-opened imine products in good to excellent yields and chemoselectivities [310]. 

The allylpalladium chloride dimer (1) has served as an excellent precursor of active catalyst for hydroamination of various substrates such as methylenecyclopropanes, enynes, and dienes. The reaction of (4-phenylbutylidene)cyclopropane with amines in the presence of 5 mol % of dimer (1) and dppp, (l,3-bis(diphenylphos-phino)propane), gave the corresponding allylic amine in 31-91% yield (eq 92). It is noteworthy that Pd precursors such as Pd2(dba)3 CHCl3, Pd(PPh3)4, or PdCl2(PPh3)2 were less efficient Pd(OAc)2 did not promote the reaction. 

Table 9 Ring-opening hydroamination of methylenecyclopropanes with group 4 metal catalysts [181]...

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