By Diego Savoia (auth.), Marc Lemaire, Pierre Mangeney (eds.)
The use of phosphine derivatives has traditionally triggered the super improvement of catalysis (both non-asymmetric and asymmetric). even if the chemistry of amines is extra documented, using nitrogen-containing ligands basically seemed lately. however, over the past ten years, the consequences describing chiral diamine arrangements and their makes use of in uneven catalysis and synthesis are expanding swifter than their phosphorus opposite numbers. The reader will locate during this quantity the newest tools for the synthesis of chiral diamines in addition to their purposes in uneven catalysis of CC bond formation. specific recognition could be given to spartein and derivatives of such diamines. lately, the actual houses and the chemistry of amines allowed to acquire catalysts effortless to split and recycle and new kinds of ligands resembling diaminocarbenes, ureas and thioureas. ultimately, the complexing homes of a few diamines allowed the formation of complexes with chirality "at the steel " that's of significant theoretical curiosity and offers various strength applications.
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Additional resources for Chiral Diazaligands for Asymmetric Synthesis
Up to now, the 1,2-diaminocyclohexanes 265–267 have been prepared from 248a, 256a and 259 through the corresponding cyclohexenes [131, 132] (Scheme 43). On the other hand, methyl substituents at C4 and C5 of the cyclohexane ring are introduced from 4,5-diamino-1,7-dienes by the reaction with in situ formed [η2 -(1-butene)]zirconocene. The relative stereochemistry of the methyl substituents was dependent on the procedure (catalytic or stoichiometric in zirconium) [133, 134]. In this way, substituted 1,2-diaminocyclohexanes 268–271 have been prepared from 248a, 256a and 256b.
After protection of the hydroxyl group in 230 to give the silyl ether 233, the imine function can be hydrogenated with opposite diastereoselectivity; see the preparation of the bicyclic aminal 234 and successively the substituted piperidine 235 [110, 111]. On the other hand, reduction of the imines 233 with lithium aluminum hydride gave the bicyclic aminals 236, from which the 2,7-disubstituted 3-aminoazepans 237 were obtained with excellent diastereoselectivity by addition of Grignard reagents .
By controlling the amount of the RLi reagent, the substitution of only one or both of the cinnamyl substituent(s) could be obtained with satisfactory to good selectivity and stereoselectivity; see the preparation of the C1 - and C2 -symmetric diamines 261a, 261b and 248a, 248c 248f, 248g, respectively. , the preparation of the C1 -symmetric 1,2-diamines 262a and 262b. Most importantly, the 4,5-diamino-1,7-octadienes 248a, 256 and 257, available by the double addition of allylic zinc reagents to the diimine 247, are Scheme 43 Synthesis of enantiopure ring-substituted 1,2-diaminocyclohexanes by transition metal catalyzed and promoted cyclization of 1,7-octadienes 50 D.