Recent applications of chiral calixarenes in asymmetric catalysis

• Mustafa Durmaz,
• Erkan Halay and
• Selahattin Bozkurt

Beilstein J. Org. Chem. 2018, 14, 1389–1412, doi:10.3762/bjoc.14.117

• % ee), which displayed the importance of the calix[4]arene skeleton. We also employed calixarene-based chiral primary amine thioureas 47a and 47b in the enantioselective Michael addition of α,α-disubstituted aldehydes 51 to maleimides 52 (Scheme 14) [50]. The reactions proceeded under mild conditions

• times with slightly decrease in its yields and diastereoselectivities. Genc et al. reported that the calixarene-based chiral tertiary amine–thioureas 55 and 56 (Scheme 15) could be used as catalyst in the asymmetric aldol reactions between 94 and 72 [53]. The aldol adducts were obtained in 79–90% yield

• addition of 48 with 49 catalyzed by 47a and 47b. Enantioselective Michael addition of 51 to 52 catalyzed by calix[4]arene thioureas. Synthesis of calix[4]arene-based tertiary amine–thioureas 54–56. Asymmetric Michael addition of 34 and 57 to nitroalkenes 49 catalyzed by 54b. Synthesis of p-tert-butylcalix

Stereoselective amine-thiourea-catalysed sulfa-Michael/nitroaldol cascade approach to 3,4,5-substituted tetrahydrothiophenes bearing a quaternary stereocenter

• Sara Meninno,
• Chiara Volpe,
• Giorgio Della Sala,
• Amedeo Capobianco and
• Alessandra Lattanzi

Beilstein J. Org. Chem. 2016, 12, 643–647, doi:10.3762/bjoc.12.63

• affording the heterocyclic products in good yields and moderate stereoselectivities. Keywords: cascade reaction; tetrahydrothiophenes; aymmetric synthesis; amine thioureas; organocatalysis; Introduction The interest toward the development of stereoselective methodologies to prepare tetrahydrothiophenes

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• will be summarized. Initially, the use of primary amine-thioureas as organocatalysts for the above transformation is being discussed, followed by the examples employing secondary amine-thioureas. Finally, the use of tertiary amine-thioureas and miscellaneous examples are presented. Keywords: multiple

• organocatalysts. Review Primary amine-thioureas as organocatalysts promoting asymmetric transformations that lead to a six-membered ring As discussed earlier, except from the activation of the substrates with the formation of the corresponding enamines or iminium ions, the synthesis of enantiopure products can be

• of a bifunctional catalyst. The first family of these bifunctional catalysts, that are going to be discussed, are the "primary amine-thioureas". Initially, catalyst 4 was studied as an organocatalyst in the addition of isobutyraldehyde (1) to (E)-methyl 2-oxo-4-phenylbut-3-enoate (2) for the

A quadruple cascade protocol for the one-pot synthesis of fully-substituted hexahydroisoindolinones from simple substrates

• Hong-Bo Zhang,
• Yong-Chun Luo,
• Xiu-Qin Hu,
• Yong-Min Liang and
• Peng-Fei Xu

Beilstein J. Org. Chem. 2016, 12, 253–259, doi:10.3762/bjoc.12.27

• -substituted hexahydroisoindolinones was developed by using bifunctional tertiary amine-thioureas as powerful catalysts. As far as we know, there is no efficient synthetic method developed toward fully-substituted hexahydroisoindolinones. The products were obtained in good yield and diastereoselectivity. The

• when K2CO3 was used as the catalyst (Table 1, entry 4). When thioureas were used as the catalysts, we also did not get the expected product (Table 1, entries 5 and 6). Since bifunctional tertiary amine-thioureas have been proved as powerful catalysts that can catalyze a variety of organocascade

Synthesis and evaluation of new guanidine-thiourea organocatalyst for the nitro-Michael reaction: Theoretical studies on mechanism and enantioselectivity

• Tatyana E. Shubina,
• Matthias Freund,
• Sebastian Schenker,
• Timothy Clark and
• Svetlana B. Tsogoeva

Beilstein J. Org. Chem. 2012, 8, 1485–1498, doi:10.3762/bjoc.8.168

• guanidine-thiourea organocatalysts would perform as well as or even better than amine-thioureas and imidazole-thioureas. Generally, guanidines are well-known basic catalysts in organic synthesis, but only scattered examples of chiral guanidines as organocatalysts are known [49]. Indeed, only one guanidine

Enantioselective Michael addition of 2-hydroxy-1,4-naphthoquinones to nitroalkenes catalyzed by binaphthyl-derived organocatalysts

• Saet Byeol Woo and
• Dae Young Kim

Beilstein J. Org. Chem. 2012, 8, 699–704, doi:10.3762/bjoc.8.78

• , bifunctional tertiary-amine thioureas, thiophosphorodiamides, and squaramide-based organocatalysts [34][35][36]. Findings In the framework of our research program for the development of synthetic methods for the enantioselective construction of stereogenic carbon centers [37][38][39][40][41][42], we recently