Amines reactions with organomagnesium

An efficient primary amine synthesis via iV-diisobutylaluminium imines has been described. A cyanide R CN (R1 = Bu, CsHn, Ph, 2-furyl or 2-thienyl) is treated with diisobutylaluminium hydride and the product is converted into the amine by reaction with an organomagnesium or organolithium compound R2M (R2 = Bu, t-Bu, allyl or benzyl)... 

Chiral aminals 1,4-dihydropyridine-3-carboxaldehydes.1 The chiral aminal 2 prepared from pyridine-3-carboxylaldehyde and (S,S)-12 reacts with organocopper reagents in the presence of methyl chloroformate to give almost exclusively products of 1,4-addition, as expected from reactions of the free aldehyde.3 No products of 1,2-addition are formed, but 1,6-adducts are minor products in some cases. The 1,4-adducts are formed in 82-93% de (R-configuration). Addition of butyl and ethyl groups is best effected with lithium cuprates, but addition of methyl, vinyl, or aryl groups is best effected with organomagnesium cuprates. Under these conditions,... 

However, systematic studies by Katritzky et al. [3] have demonstrated that reactions of 1-substituted benzotriazoles with organomagnesium compounds constitute a versatile method for substitution a to a variety of functional groups, as exemplified in Scheme 8.1. It is noteworthy that the benzotriazolyl group is displaced in preference to alkoxy (contrast the reactions of aminals noted in Section 8.2.1) and other heteroaromatic groups such as carbazolyl. The following procedure is typical. 

Alcohols, phenols, thiols and primary or secondary amines are all sufficiently acidic to donate a proton to an organomagnesium compound. The reaction with an equimolar amount of a Grignard reagent is a clean... 

Reactions of organomagnesium compounds with amines give a number of useful reagents. A preparation and use of a bromomagnesium dialkylamide has already been described (see p. 49), and others are listed in Table 10.1. (Note that in most cases the products listed in Table 10.1 were not isolated, and their constitution was not established.) The final entry in Table 10.1 is noteworthy, as bromomagnesio derivatives of pyrroles and indoles may be used as carbon nucleophiles in the synthesis of pyrrole and indole derivatives. In the case of pyrroles, N-, 2- and/or 3 substituted products may be obtained, and the conditions favouring one or another have been extensively studied [10]. In the example shown in the... 

Reactions of organomagnesium compounds with A-halogenoamines give variable proportions of halogen compounds and amines (see also Chapter 14) ... 

N-halogenation, 103 Hofmann degradation, 674 hydrolysis, 412, 415 intramolecular condensation, 576 preparation, 416, 426, 565 preparations listed in table 63, 578 reaction, with alcohols, 480 with amines, 568 with isocyanates, 647 with organomagnesium compounds, 335... 

Chiral amines have been transformed into chiral imines RCH=NG, which are usually in equilibrium with the tautomeric enamines. These enamines undergo asymmetric alkylations, and the best results are often obtained with ethers 1.58 or with valine derivatives 1.59 (R = i-Pr, R = tert-Bu) [169, 173,253] in the presence of bases. Enamines, lithioenamines and zinc enamines derived from imines are very potent Michael donors that often participate in highly stereoselective reactions [161, 162, 169, 173, 254, 257, 260, 262, 267], Chiral imines can suffer very selective addition reactions of organomagnesium reagents [139, 253, 254] and allyl-metals [154, 258]. They also suffer stereoselective Ti-catalyzed silylcyanation [268], Strecker reaction [266], and [2+2] or [4+2] cydoadditions [131, 256, 263], When the reaction produces an imine product, the chiral auxiliary is recovered after acidic hydrolysis. However, when an amine is obtained as the product, as is often the case from phenethylamine derivatives, the chiral residue is cleaved by hy-drogenolysis. In such cases, the chiral amine is not, strictly speaking, a chiral auxiliary. But these processes will be discussed anyway because of their importance in asymmetric synthesis. 

The reaction of chiral aminals of the monohydrazone of glyoxal 6.49 with organolithium reagents is stereoselective. After Raney nickel treatment, followed by protection of the amine and hydrolysis, a-aminoaldehydes are obtained with an excellent enantiomeric excess [302]. Reaction of organomagnesium reagents with 6.49 in toluene, followed by the same treatment, gives the other enantiomer [1196] (Figure 6.41). 

Summary Novel poly(silylenemethylene)s have been prepared by ring-opening polymerization of 1,3-disilacyclobutanes followed by a protodesilylation reaction with triflic acid. Reactions of the triflate derivatives with organomagnesium compounds, LiAlH4, amines or alcohols gave functional substituted and branched poly(silylene-methylene)s, which may serve as suitable precursors for silicon carbide and Si/C/N-based materials. 

Reactions of Enamine Salts with OrganometalUc Compounds Organolithium and organomagnesium compounds react with enamine salts to give amines substituted on the ix-carbon atoms. The treatment of. -dehydroquinolizidinium perchlorate (163) with alkylmagnesium halides gives 9-alkylated quinolizidines (164) (252,256). Formation of... 

Most successful approaches involving addition reactions in the presence of chiral additives utilize organolithium, organomagnesium and the recently introduced organotitanium reagents, which are known to coordinate with amines, ethers, metal amides and alkoxides. 

Methyl 2,3-epoxypropanoate can be prepared by reaction of potassium glycidate with dimethyl sulfate and one equivalent of benzyltriethylammonium chloride in methylene chloride at room temperature (65% yield).14 The reactions of this ester with organolithium or organomagnesium reagents at low temperature afford optically pure epoxy ketones14 that may be transformed via reductive amination to anti amino epoxides.15... 

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