Original Article:
A Practical Method for the Synthesis of Donor-Acceptor Cyclobutanes by Cu(OAc)2 or FeCl3 Catalyzed [2+2] Cycloaddition
Hui Luo, et al.
ChemistrySelect, 2020, 5(13): 4074-4077.
10.1002/slct.202001081
Carbocyclic and heterocyclic compounds are present in many biologically active natural products and medicinal molecules. For example, cyclobutane is present in a large number of biologically active natural products. Most of the previously reported processes for the synthesis of DA cyclobutanes required the use of purified dialkyl methylenemalonate, which was difficult to purify, reducing the practicability of the synthesis.
Herein, addressing the important issue in the chemical preparation of donor-acceptor cyclobutanes, researchers reported a practical method for the conversion of alkenes to donor-acceptor cyclobutanes under mild conditions. This method catalyzes the [2+2] addition of substituted styrenes and unpurified dialkylmethylene malonates via Cu(OAc)2 or ferric chloride (FeCl3) to obtain various DA cyclobutanes. The strategy for synthesizing DA cyclobutane is shown in scheme.
According to the range of Lewis acid-catalyzed [2+2] cycloaddition reactions (Table), relevant examples of FeCl3-catalyzed synthesis of DA cyclobutane include:
1. [c] 20 mol% FeCl3 and 3 equiv. of the crude dimethyl methylenemalona were used.
2. [d] 30 mol% FeCl3 and 3 equiv. of the crude dimethyl methylenemalona were used.
3. [e] 50 mol% FeCl3 and 4 equiv. of the crude dimethyl methylenemalona were used.
4. [f] 100 mol% FeCl3 and 4 equiv. of the crude dimethyl methylidenemalona were used, no reaction was occurred and the crude dimethyl methylidenemalonate was decomposed.
Chemicals Related in the Paper:
| Catalog Number | Product Name | Structure | CAS Number | Price |
|---|---|---|---|---|
| ACM18497671 | Ferric chloride fe 59 |  |
18497-67-1 | Price |
| ACM58694807 | Ferric chloride,dodecahydrate) |  |
58694-80-7 | Price |
