Amines from amino ethers

Chiral lithium amide bases have been used successfully in the asymmetric deprotonation of prochiral ketones [55, 56]. WUliard prepared polymer-supported chiral amines from amino acid derivatives and Merrifield resin [57]. The treatment of cis-2,6-dimethylcyclohexanone with the polymer-supported chiral lithium amide base, followed by the reaction with TMSCl, gave the chiral silyl enol ether. By using polymeric base 96, asymmetric deprotonation occurred smoothly in tetrahydrofuran to give the chiral sUyl enol ether (, S )-102 in 94% with 82% ee (Scheme 3.28). 

Miscellaneous Reactions. - p-Toluenesulfonaraide undergoes Mitsunobu-type reactions in the presence of alcohols and cyanomethylenetriphenyl-phos-phorane (56) to give predominantly mono-N-alkylation products. This reaction has also been applied to the synthesis of cyclic ethers from diols and cyclic amines from amino alcohols and to carbon-carbon bond formation. Examples of cyclic amine synthesis include that of (+)-a-skytanthine (57). A comparative study of the reactions of active methine compounds (58) as nucleophiles using... 

Amino-4 -chlorobiphenyl [135-68-2] M 203.5, m 132-133°, 134°, pK st Crystallise the amine from petroleum ether, EtOH or aqueous EtOH. The acetyl derivative has m 245° from EtOH. [Dewar James J Chem Soc 4270 1958, Gelmo Chem Ber 39 4176 1906, Beilstein 12 H 1319,12II757,12IV 3269.]... 

The formation of tluorinated Q -hydroxy-jS-imino esters (180) by treatment of fluorinated imino ethers (179) with lithium 2,2,6,6-tetramethylpiperidide has been reported. A possible explanation for this interesting intramolecular rearrangement is proposed in Scheme 64. Acyclic imides derived from primary benzylic amines and amino acid esters have been found to undergo a novel nitrogen to carbon acyl migration via a base-generated carbanion to yield the corresponding a-amino... 

Fluoro-7-nitrobenzofurazan (4-fluoro-7-nitrobenzo-2-oxa-l,3-diazole) [29270-56-2] M 183.1, m 52.5-53.5°, 53-56°, 53.5-54.5°. Purified by repeated recrystn from pet ether (b 40-60°). On treatment with MeONa in MeOH it gave 4-methoxy-7-nitrobenzo-2-oxa-l,3-diazole m 115-116°. [Nunno et al. JCS (C) 1433 1970]. It is a very good fluorophore for amino acids [Imai and Watanabe Analyt Chim Acta 130 377 7987], as it reacts with primary and secondary amines to form fluorescent adducts with 470nm and Agn, 530nm. It gives a glycine derivative with m 185-187° [Miyano et al. Analyt Chim Acta 170 81 7985]. 

In some cases, 1,1-diaminocyclopropanes may be converted to the corresponding carbinol amines. Thus, as illustrated in Scheme 17, the 7-hydroxy 7-pyrrolidinobicycloheptane 56 52b> is obtained from the diamino compound 54 in aqueous acid, and reacts with methanol or ethanol affording the corresponding amino ethers 102a,b. 89> In the presence of methyl iodide, deamination occurs and the methylhemiketal 103 is obtained (95%). 

Nevertheless, the use of chirally modified Lewis acids as catalysts for enantioselective aminoalkylation reactions proved to be an extraordinary fertile research area [3b-d, 16]. Meanwhile, numerous publications demonstrate their exceptional potential for the activation and chiral modification of Mannich reagents (generally imino compounds). In this way, not only HCN or its synthetic equivalents but also various other nucleophiles could be ami-noalkylated asymmetrically (e.g., trimethylsilyl enol ethers derived from esters or ketones, alkenes, allyltributylstannane, allyltrimethylsilanes, and ketones). This way efficient routes for the enantioselective synthesis of a variety of valuable synthetic building blocks were created (e.g., a-amino nitriles, a- or //-amino acid derivatives, homoallylic amines or //-amino ketones) [3b-d]. 

Although only a few hydrocarbons have been studied it appears that most of them react with OH with a rate constant of ca. 109 M-1 s 1. Methane is about 4 times less reactive than this value, and cyclopentane and cyclohexane about 5 times more reactive. Alcohols, amines, ethers, and many esters also fall in the same range. Carboxylic acids and carbonyl compounds seems to be to a certain degree less reactive. Lower reactivity is also found for the protonated forms of amines and amino acids. Direct reaction of OH with the substituent is usually unimportant except for a few cases such as thiols, where H is easily abstracted from the SH, or nitroso com-... 

A few effective methods have been reported for the direct formation of 8-alkyl- or 8-(hydroxy-alkyl)purines from the parent purine. These reactions are mainly photoreactions of purines with alcohols, ethers, amines, and amino acids. For a review see ref 45. 

North and co-workers required a convenient, catalytic asymmetric synthesis of specifically the (S) -enantiomer of allyHc amines [32]. They prepared a new catalyst, 17, by modifying Tomioka s tridentate amino ether la [19a], but utiHzing only readily available (S)-amino acids. Catalyst 17 was prepared in 45% yield overall from commercially available (S)-proline according to a procedure very similar to that described for the preparation of la (Scheme 10). 

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