Pentane-l,5-dial

If an unsaturated aldehyde was combined with a 1,3-dinitro compound, chiral cyclohexanes were formed by a nitro-Michael/Heniy reaction sequence. Miehael addition followed by double Heniy reaction also led to ehiral eyelohexane derivatives. In another application of the Henry re-aetion, Hayashi used nitroalkenes with pentane-l,5-dial (generated in situ) to form ehiral eyelohexane carboxaldehydes. Chiral cyclopentanes were also eonstrueted in another manner. Enamine-mediated Michael addition of aldehydes to 5-iodo-l-nitropent-l-ene led to an intermediate enamine, which underwent intramoleeular cyclisation via iodide displacement. ... 

A similar strategy was extended to the reaction of pentane-l,5-dial with aldehydes [55a], imine [55b], and alkylidene malonate [55c],... 

It also proved feasible to replace pentane-l,5-dial with alkenal 105 [56] or 2-(5-oxopentylidene) malonates [57] for a-aminoxylation/aza-Michael reactions based on a similar strategy. The a-aminoxylation of alkenal 105 with nitrosobenzene... 

The chiral Betti base 250, as a salt with L-(+)-tartaric acid, reacted with pentane-1,5-dial and benzotriazole to form diasteieopure 251 in 92% yield. Sequential replaeement of the Bt and aryloxy substituents of the piperidine ring with Grignard reagents, followed by hydrogenolytic removal of the chiral auxiliary, gave optieally pure 252 (Seheme 75) 05JOC1897>. 

A protonated O-TMS-diphenylprohnol 103/BzOH catalytic system was used by Ni et al. in an asymmetric domino Michael/Henry reaction in an aqueous medium. Chiral Michael adducts 107 generated in situ from pentane-1,5-dial (106) and (l-nitrostyrene derivatives spontaneously underwent an intramolecular Henry reaction under the proposed conditions to afford 3-substituted 2-nitro-4-formylcyclohexanols 108 containing four stereocenters in moderate to high yields and with almost complete enantioselectivity (Scheme 22.31) [116]. The catalyst could be recyded at least four times, with only a slight reduction in yields and diastereoselectivity. 

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