10.1016/j.tet.2015.05.029
The study presents a novel and environmentally friendly heterogeneous catalytic process for the synthesis of 2,3-unsubstituted benzo[b]furans, which are significant structural motifs found in natural products and biologically active molecules. The researchers utilized tin-exchanged H-b zeolite (Sn-b) as a catalyst for the intramolecular cyclization of 2-aryloxyacetaldehyde acetals, achieving good to excellent yields of a wide range of functionalized 2,3-unsubstituted benzo[b]furans. The Sn-b zeolite demonstrated excellent shape selectivity, preferentially forming 6-substituted isomers with up to 97% regioselectivity. It could be easily recovered and reused without significant loss of activity. The study's findings offer an efficient and sustainable method for the production of various benzo[b]furan derivatives, addressing the need for an improved catalyst system over traditional acidic reagents like polyphosphoric acid (PPA) and Amberlyst-15, which have limitations in terms of safety, workup procedure, and mechanical strength.
10.1021/ol302742g
The research aims to modulate the photoisomerization efficiency of N,C-chelate boryl chromophores, which are photoresponsive materials with potential applications in molecular electronics, optical data storage, molecular switching, and logic technologies. The study focuses on understanding the role of triplet acceptors, such as naphthalene, pyrene, and anthracene, in controlling the photoisomerization process and establishing the involvement of a photoactive triplet state in the isomerization of these photochromic compounds. The researchers synthesized a series of compounds (1-3) incorporating a photochromic boryl chromophore and different aromatic acceptors with varying triplet energies. They found that the photoisomerization quantum yield can be modulated by controlling the triplet energy of the acceptor, with compounds 1 and 2 undergoing quantitative conversion to their dark isomers with different quantum yields, while compound 3 showed suppressed isomerization. The study concluded that the photoisomerization of N,C-chelate dimesitylboranes likely proceeds via a triplet state, and the photoreactivity can be effectively modulated by controlling the triplet-triplet energy gap between the photochromic unit and the triplet acceptor chromophore. This finding has significant implications for the design of photochromic N,C-chelate boron compounds, suggesting that the photoisomerization can be sensitized or quenched using appropriate triplet sensitizers or acceptors.
10.1016/j.tetasy.2004.08.032
The research describes a method for the synthesis of enantiomerically pure cis- and trans-2-aminocyclohexane-1-carboxylic acids, which are significant due to their potential therapeutic applications and role in forming stable secondary structures in β-peptides. The study utilizes 2-aminobenzamide as a chiral block to assemble quinazolinone, aiming to provide a new synthesis route for all four isomers of 2-aminocyclohexanecarboxylic acid. The process involves chemoselective and diastereoselective hydrogenation of 2,3-dihydro-3-[(S)-α-methylbenzyl]-4-quinazolinone to produce octahydroquinazolinones, which can be epimerized to form their respective stereoisomers. Hydrolysis of these octahydroquinazolinones with HCl yields the desired enantiomerically pure amino acids.
10.1016/j.tet.2008.10.109
The research focuses on the development of novel gold(I)-catalyzed cascade cycloisomerization processes for the synthesis of multisubstituted 1,3-dienes and naphthalenes. The purpose of this study was to create a domino process involving a tandem sequence of 1,3- and 1,2-migrations of two different migrating groups, leading to the formation of naphthalene skeletons. The conclusions drawn from the research demonstrate that β-unsubstituted propargylic phosphates, acetates, and pivalates can undergo a mild and stereoselective gold(I)-catalyzed isomerization, resulting in the corresponding 1-oxy-1,3-diene esters. Additionally, a variety of densely substituted naphthalenes can be synthesized through a cascade cycloisomerization process. The chemicals used in these processes include propargylic esters, gold(I) catalysts such as Ph3PAuCl/AgOTf, and various substituents like methoxy, trifluoromethyl, and furyl groups. The study provides a new and efficient method for assembling naphthalenes, which were not accessible through existing methodologies.
10.1039/c3sc50643f
The study presents a method for synthesizing cyclobutane lignans and their analogs using photoinduced electron transfer. Key chemicals include oxygenated alkenes, which are used to form terminal or substituted cyclobutane adducts with complete regiocontrol and trans stereochemistry. The aromatic electron relay (ER), such as anthracene or naphthalene, is crucial for minimizing competing cycloreversion. The photooxidant 2,4,6-tris(4-methoxyphenyl)pyrylium tetrafluoroborate (p-OMeTPT) is used to excite the system and facilitate the oxidation of the alkene substrate by the ER, which then forms a cation radical capable of oxidizing the alkene. This method has been successfully applied to synthesize natural products like magnosalin and pellucidin A. The study also explores the role of the ER in preventing cycloreversion and polymerization, highlighting its importance in achieving higher yields and selectivity in the cyclobutane synthesis.
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