Secondary amines chelation

Insertion of a carbene unit into the N—H bond of primary or secondary amines by copper salt catalyzed decomposition of diazo compounds has been known for a number of years14). The copper chelate promoted reaction of diazodiphenyl-methane 291) or 2-diazo-1,2-diphenyl-1-ethanone 292) with primary benzylamines or... 

If thioamide enolates are prepared by conjugate addition of Grignard reagents to a,/3-unsaturated thioamides of secondary amines, the reaction of these enolates with aldehydes affords anti aldols. These results are rationalized by the formation of a boat-like, chelate transition state" Representative examples are provided in equation 112 and Table 16. 

The complex of Me2Zn with (5, 5 )-ebpe, 107, has been applied successfully as catalyst in the enantioselective reduction of ketones by polymethylhydrosiloxane and combines excellent product yields with high ee values . Its structure comprises the iV,iV-chelate coordination of the ebpe ligand to the MeiZn unit (Figure 51). It is remarkable that in this case the two secondary amine functionalities are coordinated to zinc and leave the Zn—C bonds unaffected. Indeed, usually secondary amines undergo a fast deprotonation reaction with dialkylzinc compounds. 

Ni(acac)2 reacts with a variety of monodentate donors giving mono and bis adducts Ni(acac)2B (n = 1,2 B = H20, primary and secondary amines, pyridine and substituted pyridines, pyridine iV-oxide, alcohols, dioxane, substituted benzaldehydes).1558,1563-1570 Details of the structures of some complexes are reported in Table 78. The chelate ring of the coordinated /3-diketones is nearly planar, and, in thl mononuclear complexes, the Ni—O bond distances (as well as the C—O and C—C bond distances within the chelate ring) are substantially similar. Two different dinuclear structures have been found in the two complexes Ni2(acac)4B [B = py (197),1540,1571,1530 Ph3AsO (198)1542,1572]. 

Simple tertiary amines are difficult to deprotonate selectively [195, 196, 200], To increase the acidity of the a-C,H-groups the amine can be quaternized [207], treated with a Lewis acid [208-211], oxidized to an amine N-oxide[161], or, for secondary amines, derivatized with a functional group capable of forming a chelate with the metal (Scheme 5.22). 

In papers published back-to-back in 1996, Hartwig and Buchwald reported amination chemistry with palladium complexes of DPPF and BINAP as catalysts [50,86]. These palladium complexes provided animations of aryl bromides and iodides with primary alkyl amines, with cyclic secondary amines, and with anilines. It is ironic that the amination chemistry was first discovered by using a particularly labile phosphine, but was dramatically improved by the use of chelating ligands. 

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