Allylic amination, asymmetric

Regioselectivity Anions of allyl silanes Anions of allyl sulfides Anions of allyl ethers Anions of allyl amines Asymmetric allylic amines Allyl Carbamates... 

A diverse group of secondary and tertiary amines are readily synthesized from the reaction of primary and secondary amines with allylic carbonates in the presence of preformed iridium metalacycles, but the direct synthesis of primary amines via iridium-catalyzed allylic amination requires the use of ammonia as a nucleophile. The asymmetric allylation of ammonia had not been reported until very recently, and it is not a common reagent in other metal-catalyzed reactions. Nonetheless, Hartwig and coworkers developed the reactions of ammonia with allylic carbonates in the presence of la generated in situ [89]. Reactions conducted in the initial work led exclusively to the products from diallylation (Scheme 16). Further advances in... 

More recently, Hartwig and coworkers reported iridium-catalyzed, asymmetric aminations of allylic alcohols in the presence of Lewis acid activators [103]. The addition of molecular sieves and Nb(OEt)5 or catalytic amounts of BPh3 activated the allylic alcohol sufficiently to allow allylic amination reactions to occur in high yield, branched-to-linear selectivity, and enantioselectivity (Scheme 29). Without the activators, only trace amounts of product were observed. 

I 9 Iridium-Catalyzed Asymmetric Allylic Substitutions Table 9.2 Ir-catalyzed asymmetric allylic aminations. 

Scheme 9.19 Asymmetric allylic amination with ammonia as nucleophile.

Scheme 9.21 Sequential intermolecular and intramolecular asymmetric allylic aminations.

Scheme 9.23 Ir-catalyzed asymmetric aminations of allylic alcohols.

Ligand Scaffold Optimization in Palladium-Catalyzed Asymmetric Allylic Amination... 

Ligand Scaffold Optimization in Palladium-Catalyzed Asymmetric Allylic Amination 245 100 I--------------------------------------------------------------------------------zr... 

Scheme 3 Asymmetric allylic amination of l,3-diphenyl-l-propene-3-acetate catalyzed by Pyrphos-palladium complexes...

A remarkable increase in catalyst selectivity was observed as a function of the dendrimer generation. This steady increase in ee values for the allylic amination was less pronounced for the PPI-derived catalysts [40% ee for PPI(PyrphosPdCl2)64] than for the palladium-PAMAM dendrimer catalysts, for which an increase in selectivity from 9% ee for the mononuclear complex to 69% ee for PAMAM(PyrphosPdCl2)64 was found. The same general trend was observed in the asymmetric allylic alkylation of 1,3-diphenyl-l-... 

Zirconaaziridines react with unsaturated C-C bonds such as (1) olefins and acetylenes [20], and with unsaturated C-X bonds such as (2) aldehydes and imines [20], (3) heterocumulenes [21,43,49],and (4) carbonates [21,22,43,50] (Scheme 5). The products generated upon workup are a-functionalized amines. Asymmetric transformations can be carried out when a chiral zirconaaziridine or inserting reagent is used optically active allylic amines and amino acid esters have been prepared, and the details of these transformations will be discussed. 

Palladium-catalyzed asymmetric allylic alkylation [529] of suitable amines with two equivalents of racemic butadiene monoxide ((-r)-411) allows for the expedient synthesis of trans-and cA-2,5-dihydropyrroles derivatives 416 and 417 that are versatile chrrons towards the s)m-thesis of a wide variety of iminosugars [530]. In the presence of 0.4% [(allyl)PdCl)2], 1.2% of enantiomerically pure diphosphine (/ ,/ )-ligand, and Na2C03 a 1 1 mixture of ( )-411 and phthalimide reacted in CH2CI2 at room temperature giving (5)-412 in 99.6% yield and... 

Table 6.2 Asymmetric allylic amination in water with 23-Pd.

Enantioselective Catalysis in Ionic Liquids 259 Table 7.10 Palladium catalyzed asymmetric allylic amination in [bdmim][ BF4]. 

Enantiomerically pure homoallylic amines are very important chiral building blocks for the synthesis of pharmacologically important molecules and natural products. The enantioselective synthesis of these compounds initially involved the chiral auxiUary-based asymmetric allylation of imines [41a, 4lb, 41c], and it is just recently that a few enantioselective variants have been reported. Although still in the regime of stoichiometric asymmetric synthesis, the first methods described below merit discussion for their synthetic utility and for establishing the groundwork for future development. 

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