Aldimines allylation

The synthesis of vinylaziridines through reactions between allylic carbenoid reagents and imines (i.e., Darzen-type reactions) was first reported by Mauze in 1980 [13]. Treatment of aldimines or ketimines 16 with gem-chloro(methyl)allyllithium (17) afforded N-substituted vinylaziridines 18 (Scheme 2.6). Similarly, 2,3-trans-N-diphenylphosphinyl-2-vinylaziridines 21 were prepared with good stereoselectivities (trans cis= 10 1 Scheme 2.7) by treatment of a-bromoallyllithium (20) with N-diphenylphosphinyl aldimines 19 in the presence of zinc chloride [14]. 

Allyltantalum-mediated allylation of aldimines was reported by Bhuyan et al. in 1993 these workers compared tantalum and bismuth organometallic reagents over a series of transformations. Up to 60% yield was obtained for tantalum-mediated allylation (benzylidene aniline as electrophile). Bismuth reagents offered better yields in the cases compared but, in all cases, a remarkable effect for the addition of Bu NBr was observed.186... 

The bismuth- or tantalum-promoted allylation of aldimines 187 (R1 = Ph or PhCH=CHCH2 R2 = Me, Ph or PhCH2) with allyl bromide in the systems Bi/Bu4N+ Br /MeCN or Ta/Bu4N+ Br /MeCN yields the amines 188193. 

Homoallylic amines result from the reaction of aldimines, previously activated by boron trifluoride etherate, with allylic bromides in the presence of chromium(II) chloride, e.g. equation 68194. 

New catalyst design further highlights the utility of the scaffold and functional moieties of the Cinchona alkaloids. his-Cinchona alkaloid derivative 43 was developed by Corey [49] for enantioselective dihydroxylation of olefins with OsO. The catalyst was later employed in the Strecker hydrocyanation of iV-allyl aldimines. The mechanistic logic behind the catalyst for the Strecker reaction presents a chiral ammonium salt of the catalyst 43 (in the presence of a conjugate acid) that would stabilize the aldimine already activated via hydrogen-bonding to the protonated quinuclidine moiety. Nucleophilic attack by cyanide ion to the imine would give an a-amino nitrile product (Scheme 10). 

Imidazoles/benzimidazoles and chiral carbinamines are of particular importance [73, 74], Recently, Leighton et al. developed a method for enantioselec-tive imidazole directed allylation of aldimines and ketimines [75] with an analogue of 31. 

In previous work, Corey used the free base form of 34 as an effective chiral ligand in the Os04-promoted dihydroxylation of olefins [90]. He later found that ammonium salt 34 catalyzed the addition of HCN to aromatic N-allyl imines (Scheme 5.50) [91]. The U-shaped pocket of the catalyst is essential in fixing the orientation of the hydrogen-bonded activated aldimine via n-n interactions. 

Scheme 6.40 Product range of the 11-catalyzed asymmetric Strecker reaction of aromatic and aliphatic N-allyl-protected aldimines.

In the presence of 42 (2mol% loading), aliphahc and aromafic N-allyl as well as N-benzyl aldimines were efficiently converted after 20 h at -70 °C in toluene to the respective Strecker adducts and subsequently trifluoroacetylated to obtain the products 1-10 in good to excellent yields (65-99%) and ee values J7-97%) (Scheme 6.41). It turned out that N-benzyl imines could be used as substrates without significant difference in comparison to analogous N-allyl imines (e.g., N-benzyl adduct 8 85% yield, 87% ee N-allyl adduct 9 88% yield, 86% ee Scheme 6.41). 

Bismuth(lll) chloride catalyzes the intramolecular hetero-Diels-Alder reaction of aldimines, generated in situ from aromatic amines and the A -allyl derivative of o-aminobenzaldehyde, in acetonitrile at reflux to generate [l,6]naphthyridine derivatives <2002TL1573>. The hetero-Diels-Alder reaction of 3-aryl-2-benzoyl-2-propeneni-triles and enol ethers yields 2-alkoxy, 6-diaryl-3,4-dihydro-2//-pyran-5-carbonitriles (Scheme 29) <1997M1157>. 

Addition of an allylic zinc reagent to cyclic aldimines has been reported129. Lithiated bisoxazoline 61 and allylzinc reagent form the reactive species, which adds to a cyclic aldimine enantioselectively with up to 97.5% (equation 29)129. 

Keywords Catalyst, Alkylation, Allylation, Arylation, Mannich reaction, Carbon-nitrogen double bond, Imine, Nitrone, Aldimine, Organozinc reagents, Silyl ketene acetal, Silyl enol ether, Amine, (3-Amino acid... 

In the presence of a Lewis acid or fluoride ion, imines react with allylsilane to yield the homoallylic amines with high stereoselectivity119,120. Thus, treatment of N-galactosylaldimine 81 with allylsilane in the presence of excess of SnCU yields the corresponding allylated product 82 (equation 54). It is noted that aliphatic aldimines do not react under these conditions. Fluoride ion promoted crotylation of aldimines proceeds in a regiospecific and diasteroselective manner121. A pentacoordinate silicate moiety is involved in this reaction. 

Amino acid synthesis (8, 389). Alkylation of the aldimine (1) from glycine ethyl ester and /j-chlorobenzaldehyde under phase-transfer conditions offers a general route to amino acids. Either liquid-liquid phase-transfer or solid-liquid phase-transfer catalytic conditions are satisfactory with active halides, but alkylation with allylic halides and less active alkyl halides is best effected under ion-pair extraction conditions (6,41), with 1 equiv. of tetra-n-butylammonium hydrogen sulfate (76-95% yields).1... 

A C2-chiral bisformamide (18) derived from diaminocyclohexane catalyses the enantioselective allylation of simple aldimines, using allyltrichlorosilane in the presence of L-proline.44 The more immediate allylating agent is, in fact, L-proline derivative (19), formed in situ, and observed by NMR and MS. 

Phenols have been employed as directing groups in the enantioselective allylation of aldimines and ketimines using allylchlorosilane reagents.45... 

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