Amides interesting examples

While the usual eonsequence of hydration of enamines is eleavage to a secondary amine and an aldehyde or ketone, numerous cases of stable carbinolamines are known (102), particularly in examples derived from cyclic enamines. The selective terminal hydration (505) of a cross-conjugated dienamine-vinylogous amide is an interesting example which gives an indication of the increased stabilization of the vinylogous amide as compared to simple enamines, which is also seen in the decreased nucleophilicity of the conjugated amino olefin-carbonyl system. 

Irimescu and Kato have recently described an interesting example of enzymatic KR in ionic liquids instead of organic solvents (Scheme 7.4) [12]. The resolution with CALB is based on the fact that the reaction equilibrium was shifted toward the amide synthesis by the removal of water under reduced pressure. Nonsolvent systems have been also employed in this enantioselective amidation processes, reacting racemic amines with aliphatic acids. The best reaction conditions for the conversion of acids to amides was observed using CALB at 90 °C under vacuum. Meanwhile, no... 

Alkanolamides from fatty acids are environmentally benign surfactants useful in a wide range of applications. It was found that most lipases catalyze both amidation and the esterification of alkanolamides however, normally the predominant final products are the corresponding amides, via amidation, and also by esterification and subsequent migration [15]. Recently, an interesting example for the production of novel hydroxyl-ated fatty amides in organic solvents has been carried out by Kuo et cd. [16]. 

There is also an interesting example of an N-CF2H amide (Scheme 4.25). 

Enantiospecific syntheses of amino derivatives of benzo[ ]quinolizidine and indolo[2,3- ]quinolizidine compounds have also been achieved via A-acyliminium ion cyclization reactions, as an alternative to the more traditional Bischler-Napieralski chemistry (see Section 12.01.9.2.2). One interesting example involves the use of L-pyroglutamic acid as a chiral starting material to construct intermediates 240 via reaction with arylethylamine derivatives. Diisobutylaluminium hydride (DIBAL-H) reduction of the amide function in 240 and subsequent cyclization and further reduction afforded piperidine derivatives 241, which stereoselectively cyclized to benzo[ ]quinolizidine 242 upon treatment with boron trifluoride (Scheme 47) <1999JOC9729>. 

An interesting example of asymmetric induction has been used for the synthesis of (—)-l from L-tryptophan. Pictet-Spengler cyclization of the corresponding amide (127) with 5-chloropentanal afforded (—)-128 as the sole product. Removal of the unwanted carboxamide function was achieved in good yield by sodium borohydride reduction of die corresponding a-amino nitrile (—)-129, resulting in (—)-l (98). 

C-H activation remains an important topic for catalysis even after thirty years of intensive research. The potential shortcuts it offers for many present routes to a wide variety of chemicals that are produced will continue to inspire industrial and academic research [32], An interesting example involves the enantiospecific, coordination-directed C-H bond functionalisation in the synthesis of a natural product, rhazinilam, an anti-tumor agent. The resulting vinyl moiety obtained in the dehydrogenation was subsequently carbonylated to form a cyclic amide [33],... 

An interesting example of an amide which appears to remain N-protonated in pure fluorosulphuric acid at low temperature is acrylamide (Farona et al., 1969). In this molecule, the carbonyl group enters into conjugation [125] with both the amino-group and... 

Another interesting example belonging to the same general principle was described by Graham (56). On one hand he prepared an amine terminated polystyrene (sodium amide initiation in liquid ammonia) and showed that it contained only one terminal primary amine group per polymer chain. On the other hand copolymers were prepared by free-radical initiated solution copolymerization of small amounts of /S-iso-cyanatoethyl methacrylate with several other monomers as methyl, butyl and lauryl methacrylates, acrylonitrile and styrene. 

Another interesting example encountering numerous applications was reported by Bolton et al It comprises the implementation of a commercially available high-loading nucleophilic resin 9 for the removal of excess starting material 2-bromobenzoyl chloride (28) during the synthesis of a simple amide such as that of A-benzyl-2-bromo-A-methylbenzamide (29), as indicated in Fig. 11. 

This is an important mechanism, and we have seen the consequences of attack by an intramolecular nucleophile (ligand) in earlier chapters. A particularly interesting example is seen in the intramolecular Michael addition of a co-ordinated amide at a cobalt(m) centre to yield an amino acid derivative (Fig. 5-44). 

Presumably, the oxidation of the iron(n) diimine complex derived from glyoxal and methylamine (encountered previously) by cerium(iv) occurs by a related mechanism (Fig. 9-37). This also provides an interesting example of the metal ion stabilising a particular tautomer of a ligand. The free ligand would be expected to exist as the amide tautomer 9.22. 

An interesting example of a branched trimer containing (1 6)- and /3(1 2)-amide-linked sugars was supplied by Sicherl and Wittmann who devised mimetics of amino glycosides [37]. Pioneered by the group of Kessler [38] pyranoid sugar amino acid templates were described to represent turn mimetics and model peptides [39,40] including cyclic peptides [41,42]. As... 

An interesting example of template synthesis is the amidomethylation of 2-(hydroxyimino) propanamide in its Niir complex, which gave the carboxamide chelate [Ni(39)] (Equation (2)).50 This is the first example of a ring-closure reaction featuring coordinated amide groups. 

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