ChemInform Abstract: [4 + 2]‐Annulations of Aminocyclobutanes.

Abstract

4 + 2]-Annulations of Aminocyclobutanes. -The first [4 + 2]-annulation between aminocyclobutanes and aldehydes to access tetrahydropyranyl amines is reported. Various tetrahydropyrans are obtained in high yields and diastereoselectivities by reaction of cyclobutane dicarboxylates and aromatic aldehydes using scandium triflate or iron trichloride as catalyst. Annulation between aminocyclobutanes and enol ethers (IV) leads to the corresponding cyclohexylamines (V). The use of thymine-or fluorouracil-substituted cyclobutanes (VI) gives direct access to six-membered ring nucleoside analogues (VII). -(PERROTTA, D.; RACINE, S.; VUILLEUMIER, J.; DE NANTEUIL, F.; WASER*, J.; Org. Lett. 17 (2015) 4, 1030-1033, http://dx.doi.org/10.1021/acs.orglett.5b00149 ; Lab. Catal. Org. Synth., Ec. Polytech. Fed. Lausanne, CH-1015 Lausanne, Switz.; Eng.) -S. Adam

A Practical Method for the Synthesis of Donor‐Acceptor Cyclobutanes by Cu(OAc)2 or FeCl3 Catalyzed [2+2] Cycloaddition

“…After that, the formal [4 + n] cycloaddition reactions of DÀ A cyclobutanes with various dipolarophiles such as aldehydes, imines, alkenes, nitrones, and indoles, emerged and attracted much attention. [1b,g, h, j, 4] For instance, Christie, [5] Johnson, [6] Pagenkopf, [7] Waser, [8] Matsuo [9] and Tang group [10] have developed effective approaches to construct various formal [4 + n] cyclic compounds, respectively.…”

“…After that, the formal [4 + n] cycloaddition reactions of DÀ A cyclobutanes with various dipolarophiles such as aldehydes, imines, alkenes, nitrones, and indoles, emerged and attracted much attention. [1b,g, h, j, 4] For instance, Christie, [5] Johnson, [6] Pagenkopf, [7] Waser, [8] Matsuo [9] and Tang group [10] have developed effective approaches to construct various formal [4 + n] cyclic compounds, respectively.Dialkyl methylidenemalonates are very reactive and sensitive compounds, [11] have been used in [2 + 2] cycloadditions with electron-rich alkenes to form DÀ A cyclobutanes in the presence of Lewis acid catalysts at À 78 °C (Scheme 1a). [6,7b, 12] Recently, Waser group developed an FeCl 3 ⋅Al 2 O 3 -catalyzed [2 + 2] cycloaddition reactions of enimides and alkylidene malonates, giving aminocyclobutanes in excellent yields (Scheme 1b).…”