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Phosphine-catalyzed intramolecular formal [3+2] cycloaddition for highly diastereoselective synthesis of bicyclo[n.3.0] compounds.
| Content Provider | Semantic Scholar |
|---|---|
| Author | Ye, Long-Wu Sun, Xiu-Li Wang, Qinggang Tang, Yong |
| Copyright Year | 2007 |
| Abstract | Ylides have been widely applied in constructing small-ring compounds such as epoxides, cyclopropanes, and aziridines. Recently, several ylide cyclizations that go beyond the formation of three-membered rings have also been developed. Lu and co-workers demonstrated in a number of elegant studies that phosphines are good catalysts for the construction of cyclopentenes. Krische and co-workers developed the first intramolecular variant of the cycloaddition. Catalytic asymmetric [3+2] cycloadditions have been reported by both Zhang and Fu, with their respective coworkers. Recently, Aggarwal and co-workers documented an elegant protocol for the asymmetric synthesis of epoxideand aziridine-fused heterocycles through a sulfur ylide route. In a previous study on ylide chemistry, we reported a tandem ylide Michael addition–elimination–substitution reaction for the controllable synthesis of 2H-chromenes 2a and 4H-chromenes 2a’ (Scheme 1). To further extend the reaction scope, 3a was synthesized and subjected to the reaction. However, the desired compound 4a’was obtained in only 15% yield under the same conditions. To improve the yield, other potential catalysts such as PPh3 and 1,4diazabicyclo[2.2.2]octane (DABCO) were tested instead of THT. When triphenylphosphine was used, the bicyclic compound 4a was, unexpectedly, isolated as the sole product in 30% yield with excellent diastereoselectivity (Scheme 1). Herein, we wish to report the preliminary results of this cyclization. Further studies showed that the desired product was not observed in the absence of PPh3. In the presence of PPh3 (20 mol%) with Na2CO3 as a base, bromide 3b afforded the corresponding benzobicyclo[4.3.0] compounds (4b/4b’) in 95% yield with excellent diastereoselectivity (entry 1, Table 1). To study the generality of the current reaction, |
| File Format | PDF HTM / HTML |
| DOI | 10.1002/anie.200701460 |
| Alternate Webpage(s) | http://tangyong.sioc.ac.cn/upfile/29.2007-yelongwu-Angew.%20Chem.%20Int.%20Ed.%202007,%2046,%205951.pdf |
| PubMed reference number | 17582807 |
| Alternate Webpage(s) | https://doi.org/10.1002/anie.200701460 |
| Journal | Medline |
| Volume Number | 46 |
| Issue Number | 31 |
| Journal | Angewandte Chemie |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
