Catalytic Activation of C−H and C−C Bonds of Allylamines via Olefin Isomerization by Transition Metal Complexes

Abstract

The metal-catalyzed reaction of olefins with allylamines bearing coordination sites (2-pyridyl groups) was studied. With Ru 3 (CO) 12 as catalyst, activation of C−H bonds led to the formation of ketimines that were hydrolyzed to give asymmetric ketones. With [(C 8 H 14 ) 2 RhCl] 2 , both C−H and C−C bonds were activated and symmetric ketones were formed on hydrolysis. The reaction involves double bond migration of the allylamine to form an aldimine.Catalytic activation of C-H 1,2 and C-C 3,4 bonds has a broad impact in organometallic chemistry because of its applications in organic synthesis. Aldehydic C-H bond activation 5 and chelation-assisted hydroacylation 6 were described earlier.In particular, the use of 2-amino-3-picoline avoids decarbonylation effectively. 7 Activation of the C-C bond in ketones bearing β-hydrogen using chelation assistance has also been documented. 8 Aldimines and ketimines are postulated intermediates for these C-H and C-C bond activations. Catalytic activation of aromatic aldehydes with 2-amino-3-picoline is more efficient than activation of aliphatic aldehydes. 7a,9 The formation of aminal side products during the reaction with aliphatic aldehydes reduces the yields. Double bond migration of allylamines in the presence of transition metal complexes provides a versatile approach to the preparation of aldimines of the aliphatic alkyl group. 10

Metal–Organic Cooperative Catalysis in C–C Bond Activation

“…In 75, C-H and C-C bonds exist α to the imine moiety and, as a result, activation of both of these bonds enables this substance to serve as a synthetic surrogate of formaldehyde (Scheme 13a). Accordingly, treatment of allylamine 74 and olefin 47 with a catalytic amount of rhodium catalyst (66/67) leads to formation of the symmetric dialkyl ketone 77 along with a small amount of ketone 76 (Scheme 13b) [31]. In this process, 74 is first transformed to the corresponding imine 75, which then undergoes chelation-assisted hydroimination in the presence of Rh(I) catalyst to produce ketimine 54.…”

Intermolecular Hydroacylation by Transition‐Metal Complexes

“…Since aldimines can be generated in situ through double bond migration in allylamines in the presence of transition-metal complexes, allylamine is also a good substrate for hydroacylation (Scheme 24). [62] For example, allylamine 72 reacted with tert-butylethylene (73) in the presence of a [Ru 3 (CO) 12 ] catalyst to give ketone 74 in a high yield after hydrolysis (Scheme 24). However, when the reaction was performed in the presence of the rhodium(I) catalyst and the PCy 3 (tricyclohexylphosphane) ligand, symmetric dialkyl ketone 75 was obtained in high yield along with a small amount of 74 in a 95:5 ratio (Scheme 24).…”

Di-μ-Chlorobis[Bis-(cyclooctene)rhodium]

“…Also, symmetrical acyclic ketones can be made under analogous conditions by reacting allylamine 18 with an excess of a terminal mono-alkene such as 1-hexene. 29 The reactions are postulated to proceed by the complicated sequence of events as summarized in Scheme 4 for the reaction of 3,3-dimethyl-1,4-pentadiene with 18. Thus, rhodium-catalyzed alkene isomerization of 18 gives the aldimine 19, which reacts by directed hydroiminoacylation (as outlined in eq 3) to produce Hydrogenation.…”