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An unprecedented Ag‐catalyzed exo′‐selective [3+2] cycloaddition of imino esters with 4‐benzylidene‐2,3‐dioxopyrrolidines is described. The reaction was efficiently catalyzed by Ag/(R, Sp)‐ThioClickFerrophos (TCF) leading to the construction of the corresponding spirobipyrrolidine scaffolds in excellent enantio‐ and diastereoselectivities. This reaction is the first example of a silver‐catalyzed exo′‐selective asymmetric [3+2] cycloaddition, as well as the first exo′‐selective spirobipyrrolidine construction via a [3+2] cycloaddition process using imino esters. The wide substrate scope of this reaction enabled the preparation of structurally diverse spirobipyrrolidine derivatives, which are attracting attention as targets for drug discovery. Mechanistic studies suggested that the unusual exo′‐selectivity of this reaction is not due to epimerization following the common exo‐ or endo‐selective cycloaddition, but instead is due to a stepwise Michael addition/Mannich sequence with bond rotation. [ABSTRACT FROM AUTHOR]

New phosphors with various emission colors for RE3+ doped Li1+xTa1-xTixO3 (LTT) (RE: Eu, Sm, Er, Tm, and Dy) were synthesized by electric furnace at 1423 K for 15 h. The microstructure of the host material and the photoluminescence (PL) property were determined and compared to those of RE3+ doped Li1+xNb1-xTixO3 (LNT). In the LTT phosphor, the highest PL intensity was achieved for the mixture composition Li1.11Ta0.89Ti0.11O3 with a LiTaO3 structure, although it has an M-phase superstructure. In the LTT host material, the effective activators were Eu3+ and Sm3+ ions, in contrast to the LNT host material. Here, we discuss the relationship between PL property and the host material's structure. [ABSTRACT FROM AUTHOR]

The stereodivergent asymmetric synthesis of 2,5-trans/cis pyrrolidines by 1,3-dipolar cycloaddition using two different types of activated alkenes is described. When ylidene-isoxazolones were employed as dipolarophiles, the Ag/(S,S p )-iPr-FcPHOX-catalyzed asymmetric [3+2] cycloaddition of imino lactones proceeded with 2,5-trans selectivity. Subsequent decarboxylation of the isoxazolone rings produced pyrrolidines with 2,5-trans stereoretention. In the reaction using acyclic enones as activated alkenes, the Ag/(R,S p )-ThioClickFerrophos complex-catalyzed asymmetric [3+2] cycloaddition afforded 2,5-cis substituted pyrrolidines in high yields and enantioselectivities. Therefore, these methods can be considered as a formal stereodivergent synthesis of 2,5-cis/trans pyrrolidines., (© 2023 Wiley-VCH GmbH.)

New phosphors with various emission colors for RE 3+ doped Li 1+ x Ta 1- x Ti x O₃ (LTT) (RE: Eu, Sm, Er, Tm, and Dy) were synthesized by electric furnace at 1423 K for 15 h. The microstructure of the host material and the photoluminescence (PL) property were determined and compared to those of RE 3+ doped Li 1+ x Nb 1- x Ti x O₃ (LNT) . In the LTT phosphor, the highest PL intensity was achieved for the mixture composition Li 1.11 Ta 0.89 Ti 0.11 O₃ with a LiTaO₃ structure, although it has an M-phase superstructure. In the LTT host material, the effective activators were Eu 3+ and Sm 3+ ions, in contrast to the LNT host material. Here, we discuss the relationship between PL property and the host material's structure.