3- Aminocyclohex-2-enone

The same pathway is traced in the reaction of o-aminobenzaldehyde, which with 4-methoxybut-3-en-2-one forms 2-methylquinoline-3-carbaldehyde dimethylac-etal (231) (80MI1). With 3-aminocyclohex-2-enone it gives tetrahydroquinolinone 232 in 72% yield (76BRP1432579). 

Later, Tu and coworkers [57] reported domino synthesis of furo[3,4-h][l, Sjnaphthyridines 93 through three-component reactions of aldehydes 69, 2-aminoprop-l-ene-l,l,3-tricarbonitrile 29, and N-substituted 4-aminofuran-2(5H)-ones 57 in EtOH using EtONa as a base (Scheme 12.36). N-substituted 3-aminocyclohex-2-enones were also suitable for this domino reaction, affording 21 examples of benzo[h][l,8]naphthyridines in 69-84% chemical yield, with the concomitant formation of two new pyridine rings. 

Recently, Tu, Li, and coworkers [58] described the first domino [4-1-1]/ [3- -2- -l]/[5- -l] and double [4-1-3] cyclization reactions of o-phthalaldehyde 94 and 4-hydroxy-6-methyl-2H-pyran-2-one 95 with N-substituted enaminones 57 (Scheme 12.37). Using N-substituted 3-aminocyclohex-2-enones as enaminone led to pentacyclic pyrano[3, 2 2,3]indeno[2,l-c]pyridines 96 in 44-68% yield, whereas by employing N-substituted 4-aminofuran-2(5H)-ones the reaction occurred in another direction to form multifunctionalized pentacyclic pyrano[4,3- j]oxepines 97. This work provides an attractive strategy for the construction of structurally diverse pentacyclic oxa-azaspiro and oxa-azabridged skeletons. 

Tu, Li, and coworkers also developed a new allylic functionalization without the use of metal catalysts [59-61]. Efficient annulation of enaminones 57 with arylglyoxal monohydrates 58 and the subsequent allylic functionalization with aliphatic carboxylic acids 38 as nucleophile reagents provided multifunctionalized indoles 98 with 75-89% yields (Scheme 12.38) [59]. To further explore the scope of this domino reaction, N-substituted 3-aminocyclohex-2-enones were employed. Interestingly, two molecules of arylglyoxal mono hydrate and N-substituted... 

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