Cycloaddition reactions acylhydrazones

Inspired by the previous results, Leighton et al. reported the enantioselective [3 + 2] acylhydrazone-enol ether cycloaddition reaction by employing the same pseudoephedrine-based chiral silane. The pyrazohdine product was obtained in 61% yield with 6 1 dr and 77% ee in 24 h. The use of tert-butyl vinyl ether led to an improvement in both diastereoselectivity and enantioselectivity as shown in Scheme 34 [108]. 

The ability of related acylhydrazones 94 (Scheme 24), derived from a,/3-unsaturated aldehydes, to participate in intramolecular Diels-Alder cycloaddition reactions has been proven to occur by Gilchrist and coworkers (91TL125). They reported that azadiene 94 (n = 1) cyclized to 95, whereas compound 94 (n = 0) did not undergo intramolecular cycload-... 

Acryloyl isocyanates, reaction with amino-sugars, uridine analogs from, 55, 139 A-Acyldehydroaminoacids, addition of nucleophiles, 57, 230 Acylhydrazones, a/3-unsaturated, cycloadditions, 57, 14 A-Acyliminium (ions), generation from alkylidenepiperazine-2,5-diones, 57, 230... 

Kobayashi and coworkers have reported that the [3 + 2] cycloaddition between hydrazones (23) and olefins is accelerated in the presence of a stoichiometric amount of BF3 OEt2, under mild conditions affording cyclic five-membered ring compounds (Equation 17) [23]. The reaction of acylhydrazone with cyclopentadiene gives the expected product (24) in high yield and reasonable diastereomeric ratio. 

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See also in sourсe #XX -- [ ]

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