10.1021/ol702455v
The research focuses on the gold-catalyzed intramolecular carbocyclization of alkynyl ketones, leading to the formation of highly substituted cyclic enones. The study explores the use of coinage metal salts, particularly AuCl3 and AgSbF6, as π-electrophilic Lewis acids to activate alkynes for nucleophilic attack, facilitating the formation of new C-C and C-heteroatom bonds. The experiments involved the optimization of reaction conditions for the transformation of internal alkynyl ketones into tetrasubstituted cyclic enones, with a series of cationic coinage metal catalysts tested in toluene at 100°C. The reactants included internal alkynyl ketones with various substituents, and the analyses used to determine the yields and structures of the products were 1H NMR spectroscopy and isolated yields of products 2. The study also proposed a plausible mechanism for the gold-catalyzed carbocyclization process.
10.1055/s-0040-1707289
The study focuses on the development and investigation of Pentamethylphenyl (Ph*) and its derivatives as acyl protecting groups in organic synthesis. Protecting groups are crucial in organic chemistry as they prevent certain functional groups from reacting, allowing for the selective modification of others. The Ph* group, due to its unique 2,6-disubstitution pattern, provides a 'twisting effect' that shields the carbonyl group from nucleophilic attack, which is beneficial for reactions like hydrogen borrowing. However, the study initially faced challenges in removing the Ph* group without affecting sensitive functional groups present in the molecule. To address this, various reagents and conditions were explored, including Br2, TMSCl, n-BuOH, HFIP, and AuCl3, among others. These chemicals served to either facilitate the cleavage of the Ph* group or to modify the Ph* itself (PhOH) to make it more reactive towards electrophiles, thereby enabling the deprotection of a range of carbonyl compounds without compromising the integrity of the molecule. The study also investigated the compatibility of these reagents with different functional groups and provided alternative approaches for challenging substrates, contributing to the broader understanding and application of Ph as a protecting group in organic synthesis.
10.1002/chem.200903419
The research investigates the gold-catalyzed cyclization of 1-epoxy-1-alkynylcyclopropanes to produce a diverse array of complex oxacyclic products. Key chemicals involved in this study include cis-epoxides 1a and 1b, as well as their trans isomers 3a and 3b, which were used as substrates to illustrate the effect of epoxy substituents on the gold-catalyzed oxacyclization process. Gold(III) chloride (AuCl3) served as the catalyst, while water was used as a co-reagent. The study also utilized various dienes, such as 2,3-dimethylbutadiene, and enones like pent-1-en-3-one and oct-1-en-3-one, to achieve [4+2] cycloaddition reactions with the generated 1-oxyallyl cations. The resulting products, including bicyclic oxacyclic alcohols 2a and 2b, tricyclic compounds 5a and 6a, and other oxacyclic compounds like 7a–7d and 8, were characterized using techniques such as 1H NOE spectroscopy. The research highlights the stereoselectivity and diastereoselectivity of the gold-catalyzed reactions, particularly noting the high stereoselectivity observed with cis-epoxides compared to their trans analogues.