Arylation imines

Scott et al. [45] prepared diimine derivatives of 2,2 -diamino-6,6 -dimethyl-biphenyl (as structure 37 in Scheme 19) as copper chelates for the catalyzed cyclopropanation reaction. All catalysts were active in this reaction but enan-tioselectivities varied importantly according to the substitution pattern of the imine aryl group only ortho-substituted ligands (by chloride or methyl groups) led to products with measurable enantioselectivity for the model test reaction (up to 57% ee with 37). 

In another reaction, alkynyl groups were transferable in the presence of a catalytic amount of Me3Al (Equation (78)).279 Preference for the Ph group transfer has been well featured in the competitive alkyl transfer process leading to selective imine arylation (Equation (79)). Higher organic chains such as ethyl and butyl are... 

With the PBI catalysts, the incorporation of ligands with significantly reduced bulk, typically only a single ortho substituent on the imine aryl group, and the absence of chain walking produces high-quality a-olefins. The PBI oligomerization catalysts are extremely productive, even relative to the polymer-... 

The in situ formation of a ketimine provided the cyclization precursor, which furnished on imine arylation the densely functionalized dibenzodiazepine derivative (Scheme 13.96). When the keto functionality was replaced by an ester moiety, which is reactive toward ammonia under the reaction conditions, an amide cyclization precursor is generated in situ (Scheme 13.97). The arylation of the spawned amide by the aryl chloride fragment furnished the dibenzoxazepinone derivatives in good to excellent yields. 

With Rhodium In 2010, the groups of Ellman and Bergman [47] reported the Rh(III)-catalyzed aryla-tion of Boc-Imines (see Chapter 6, for imine arylation) via C-H bond functionalization (Figure 4.22). This in fact was a very interesting method for the synthesis of chiral amines, being complementary to the variety of aryl boronic acid methods that are currently known [48]. 

Ru has been used frequently for obtaining chiral amine units, in asymmetric transfer hydrogenations of imine substrates [40], aldol-type reactions with imine electrophiles [41], and C-H bond arylation (see Chapter 4) [42]. There are very few reports in the literature on the use of ruthenium cattilysts for imine arylation. 

As far as we are aware, there have been no other reports on the arylation of imine substrates with ruthenium catalysts, besides our own work. In 2012, we published our efforts at developing a Ru-catalyzed asymmetric catalytic imine arylation with organoboron reagents and with chiral phosphane and new NHC-type ligands (Scheme 6.33) [44]. 

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