Chiral multifunctional thiourea-phosphine catalyzed asymmetric [3 + 2] annulation of Morita–Baylis–Hillman carbonates with maleimides

• Hong-Ping Deng,
• De Wang,
• Yin Wei and
• Min Shi

Beilstein J. Org. Chem. 2012, 8, 1098–1104, doi:10.3762/bjoc.8.121

• (MBH) carbonates with maleimides, which can efficiently construct functionalized cyclopentenes bearing three contiguous stereocenters in moderate to excellent yields and excellent diastereo- and enantioselectivities. A plausible mechanism has been also proposed on the basis of control experiments and

• previous literature. Keywords: asymmetric [3 + 2] annulation; maleimides; Morita–Baylis–Hillman carbonates; multifunctional thiourea-phosphine; organocatalysis; Introduction Highly functionalized cyclopentene derivatives are important subunits in a variety of biologically active molecules and have

• + 2] annulation of MBH carbonates with maleimides, which can efficiently construct functionalized cyclopentene derivatives bearing three contiguous stereocenters in moderate to excellent yields along with excellent diastereo- and enantioselectivities. Results and Discussion In our previous work, it

Expanding the chemical diversity of spirooxindoles via alkylative pyridine dearomatization

• Chunhui Dai,
• Bo Liang and
• Corey R. J. Stephenson

Beilstein J. Org. Chem. 2012, 8, 986–993, doi:10.3762/bjoc.8.111

• , spiro [1,3]oxazino compounds having a diene moiety within their molecular framework are susceptible to Diels–Alder (D–A) reactions [22]. Scheme 2 highlights three examples in which compound 3a was exposed to N-substituted maleimides in toluene at 150 °C under microwave irradiation for 0.5 h, and D–A

C₂-symmetric bisamidines: Chiral Brønsted bases catalysing the Diels- Alder reaction of anthrones

• Deniz Akalay,
• Gerd Dürner,
• Jan W. Bats and
• Michael W. Göbel

Beilstein J. Org. Chem. 2008, 4, No. 28, doi:10.3762/bjoc.4.28

• Brønsted bases in the Diels-Alder reaction of anthrones and N-substituted maleimides. High yields of cycloadducts and significant asymmetric inductions up to 76% ee are accessible. The proposed mechanism involves proton transfer between anthrone and bisamidine, association of the resulting ions and finally

• a cycloaddition step stereoselectively controlled by the chiral ion pair. Keywords: Asymmetric Catalysis; Bisamidines; Brønsted base; Diels-Alder reaction; Organocatalysis; Introduction The cycloadditions of anthrones 1 and N-substituted maleimides 2 are prominent examples of asymmetric catalysis

• base catalysts in the cycloaddition of anthrones 1 and maleimides 2. Results and Discussion Analogous to the synthesis of compound 8a [6], the other bisamidines were prepared as hydrochlorides in 60–79% yield from the corresponding chiral diamines 9 and bisimidate 10 in refluxing ethanol. Simple