| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1997: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1996: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
The hetero Diels-Alder reaction using carbonyl compounds as dienophiles has been a very useful method to construct the dihydropyran skeleton. However, it is necessary to use activated dienes containing strong electron-donating groups and/or activated carbonyl compounds containing electronwithdrawing groups to conduct the reaction smoothly under mild conditions. In this research project, we found that the hetero Diels-Alder reaction of nonactivated simple dienes with aldehydes is catalyzed by cationic palladium (II) complexes. Thus, the reaction of 2-methyl and 2,3-dimethyl substituted 1,3-butadienes with aromatic and aliphatic aldehydes proceeded smoothly at 50ﾟC for 20 h in the presence of 2 mol% of the cationic palladium (II) complexes, such as [Pd (dppp) (PhCN) _2] (BF_4) _2. In this reaction, we assume that the palladium complex acts as a Lewis acid catalyst. In the research of 1997, we investigated asymmetric hetero Diels-Alder reaction using chiral palladium complex. The reaction of phenylglyoxal with 2,3-dimethyl-1,3-butadiene, 1,3-cyclohexadiene, and 1,2-dimethylenecyclopentane in the presence of [Pd (S-BINAP) (PhCN) _2] (BF_4) _2 afforded the cyclization products in 95 to 99 %ee, respectively. It can be assumed that chelate coordination of the two carbonyl group of phenylglyoxal to palladium give rise to the high enantioselectivity.
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