1,4-Additions of the highly functionalized copper reagents RCu(CN)ZnI · 2 BFP3 to trisubstituted enones. A new BF3 promoted cyclization reaction
✍ Scribed by Ming Chang P. Yeh; Paul Knochel; William M. Butler; Scott C. Berk
- Publisher
- Elsevier Science
- Year
- 1988
- Tongue
- French
- Weight
- 208 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0040-4039
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✦ Synopsis
The new copper reagents RCu(CN)Zn I .2 BF3 1 containing various functional groups like esters, cyanides, chlorides or enoates react with p, P'-disubstituted enones to afford the Michael adducts 4-7 in high yields (81-98%). Cyano-substituted 1,4-adducts undergo a new cyclization reaction leading to the very stable bicyclic difluoroboron enolates lla-llc which could be converted into the bicyclic diketones 12 under mild basic conditions. The X-ray structure of llb is reported.
Recently, we reported1 that the highly functionalized copper, zinc organometallics FG-R-Cu(CN)ZnI 1 obtained from the corresponding alkylzinc iodides 2 react with various electrophiles like acyl chlorides, allylic halides, aldehydes or enones to afford polyfunctional molecules in high yields. However a p, p'-disubstituted enone like 3-methyl-2cyclohexen-l-one gave the desired 1,4-adduct in only a moderate yieldla.
We wish now to report that the presence of BF3 .OEt22 allows us to perform Michael additions of the organo-copper reagents 1 to highly substituted enones 3 in excellent yields @l-98%). See Scheme 1 and Table 1.