Organolathanide-catalyzed regioselective intermolecular hydroamination of alkenes, alkynes, vinylarenes, Di- and trivinylarenes, and methylenecyclopropanes. Scope and mechanistic comparison to intramolecular cyclohydroaminations

Organolanthanide complexes of the type CP'(2)LnCH(SiMe3)(2) (Cp' = eta(5)-Me5C5; Ln = La, Nd, Sm, Lu) and Me2SiCP"(2)LnCH(SiMe3)(2) (Cp" = eta(5)-Me4C5; Ln = Nd, Sm, Lu) serve as efficient precatalysts for the regioselective intermolecular hydroamination of alkynes R'CdropCMe (R' = SiMe3, C6H5, Me), alkenes RCH=CH2 (R = SiMe3, CH3CH2CH2), butadiene, vinylarenes ArCH=CH2 (Ar = phenyl, 4-methylbenzene, naphthyl, 4-fluorobenzene, 4-(trifluoromethyl)benzene, 4-methoxybenzene, 4- (dimethylamino) benzene, 4-(methylthio)benzene), di- and trivinylarenes, and methylenecyclopropanes with primary amines R"NH2 (R" = n-propyl, n-butyl, isobutyl, phenyl, 4-methylphenyl, 4-(dimethylamino)phenyl) to yield the corresponding amines and imines. For R = SiMe3, R = CH2=CH lanthanide-mediated intermolecular hydroamination regioselectively generates the anti-Markovnikov addition products (Me3SiCH2CH2NHR", (E)-CH3CH=CHCH2NHR"). However, for R = CH3CH2CH2, the Markovnikov addition product is observed (CH3CH2CH2CHNHR"CH3). For internal alkynes, it appears that these regioselective transformations occur under significant stereoelectronic control, and for R' = SiMe3, rearrangement of the product enamines occurs via tautomerization to imines, followed by a 1,3-trimethylsilyl group shift to stable N-SiMe3-bonded CH2=CMeN(SiMe3)R" structures. For vinylarenes, intermolecular hydroamination with n-propylamine affords the anti-Markovnikov addition product beta-phenylethylamine. In addition, hydroamination of divinylarenes provides a concise synthesis of tetrahydroisoquinoline structures via coupled intermolecular hydroamination/subsequent intramolecular cyclohydroamination sequences. Intermolecular hydroamination of methylenecyclopropane proceeds via highly regioselective exo-methylene C=C insertion into Ln-N bonds, followed by regioselective cyclopropane ring opening to afford the corresponding imine. For the Me2SiCP"Nd-2-catalyzed reaction of Me(3)SiCdropCMe and H2NCH2CH2CH2CH3, DeltaH(double dagger) = 17.2 (11) kcal mol(-1) and DeltaS(double dagger) = -25.9 (9.7) eu, while the reaction kinetics are zero-order in [amine] and first-order in both [catalyst] and [alkyne]. For the same substrate pair, catalytic turnover frequencies under identical conditions decrease in the order Me2SiCP"2NdCH(SiMe3)(2) > Me2SiCP"2SMCH(SiMe3)(2) > Me2SiCP"2LuCH(SiMe3)(2) > CP'2SmCH(SiMe3)(2), in accord with documented steric requirements for the insertion of olefinic functionalities into lanthanide-alkyl and -heteroatom sigma-bonds. Kinetic and mechanistic evidence argues that the turnover-limiting step is intermolecular C=C/CdropC bond insertion into the Ln-N bond followed by rapid protonolysis of the resulting Ln-C bond.