25570-44-9Relevant academic research and scientific papers
Highly Stereoselective Positional Isomerization of Styrenes via Acid-Catalyzed Carbocation Mechanism
Hu, Xiao-Si,He, Jun-Xiong,Zhang, Ying,Zhou, Jian,Yu, Jin-Sheng
supporting information, p. 2227 - 2233 (2021/06/28)
The first transition metal-free highly stereoselective positional isomerization of various α-alkyl styrenes through a carbocation mechanism triggered strategy is developed by using Al(OTf)3 as a hidden Br?nsted acid catalyst, which provides facile access to value-added acyclic tri- and tetra-substituted alkenes in good yields with high stereoselectivity under mild conditions. The practicality of this protocol is further highlighted by the gram-scale synthesis, high stereoselectivity, good functional group tolerance, and simple operation. Mechanistic studies support that Al(OTf)3 acts as a hidden Br?nsted acid catalyst and a carbocation intermediate is formed.
Extending the Substrate Scope in the Hydrogenation of Unfunctionalized Tetrasubstituted Olefins with Ir-P Stereogenic Aminophosphine-Oxazoline Catalysts
Biosca, Maria,Salomó, Ernest,De La Cruz-Sánchez, Pol,Riera, Antoni,Verdaguer, Xavier,Pàmies, Oscar,Diéguez, Montserrat
supporting information, p. 807 - 811 (2019/01/26)
Air-stable and readily available Ir-catalyst precursors modified with MaxPHOX-type ligands have been successfully applied in the challenging asymmetric hydrogenation of tetrasubstituted olefins under mild reaction conditions. Gratifyingly, these catalyst precursors are able to efficiently hydrogenate not only a range of indene derivatives (ee's up to 96%) but also 1,2-dihydronapthalene derivatives and acyclic olefins (ee's up to 99%), which both constitute the most challenging substrates for this transformation.
Dual Intermolecular Allylic C–H Functionalization of the Tetrasubstituted Alkene Scaffold
Martínez, Claudio,Mu?iz, Kilian
, p. 1248 - 1254 (2018/03/21)
Activation of chloramine-T (TsNNaCl) with a Br?nsted acid generates an active reagent for the double allylic C–H functionalization of tetrasubstituted alkenes in an intermolecular manner. The reaction generates a carbon–nitrogen and a carbon–chlorine bond, and proceeds with complete regio- and chemoselectivity. A total of 14 examples demonstrate the applicability of the dual C–H functionalization process. The mechanism involves the intermediacy of a 1,3-butadiene derivative; 1,3-butadienes can also be used directly as substrates.
(5,6-Dihydro-1,4-dithiin-2-yl)methanol as a Versatile Allyl-Cation Equivalent in (3+2) Cycloaddition Reactions
Hullaert, Jan,Winne, Johan M.
supporting information, p. 13254 - 13258 (2016/10/30)
The title heterocyclic alcohol readily generates a sulfur-substituted allylic cation upon simple treatment with a protic acid, thus facilitating a synthetically useful stepwise (3+2) cycloaddition reaction pathway with a range of conjugated-olefin-type substrates. The introduction of an allyl fragment in this way provided rapid access to a variety of cyclopentanoid scaffolds. The cyclic nature of the cation precursor alcohol was shown to be instrumental for efficient cycloaddition reactions to take place, thus indicating an attractive strategy for controlling the reactivity of heteroatom-substituted allyl cations. The formal cycloaddition reaction is highly regio- and stereoselective and was also used for a short total synthesis of the natural product cuparene in racemic form through a cycloaddition–hydrodesulfurization sequence.
Substituent Effects upon Efficiency of Excited-State Acetophenones Produced on Thermolysis of 3,4-Diaryl-3,4-dimethyl-1,2-dioxetanes
Richardson, William H.,Stiggal-Estberg, Diana L.,Chen, Zhangping,Baker, John C.,Burns, David M.,Sherman, David G.
, p. 3143 - 3150 (2007/10/02)
The effects of meta and para substituents upon the triplet (αT) and singlet (αS) efficiencies in the thermolysis of 3,4-diaryl-3,4-dimethyl-1,2-dioxetanes 3, 3-aryl-3,4,4-trimethyl-1,2-dioxetanes 4, and 3-aryl-3-(bromomethyl)-4,4-dimethyl-1,2-dioxetanes 5 are reported.Triplet efficiencies for series 3 dioxetanes, where the two proketone moieties are identical, are sensitive to aryl substituent changes.Attempted correlation of log αT with Hammett-type substituents constants failed, and the best correlation of log αT was with the lowest triplet energy of the acetophenones T) = (0.77+/-0.19)ET1(ArCOCH3)-55.05+/-14.00, r=0.834, Sy*x=+/-0.336>.This type of correlation was previously observed with 3-aryl-3-methyl- and 3-aryl-3-methyl-3,3-(2,2'-biphenyldiyl)-1,2-dioxetanes, where the slopes (S values) are 0.38+/-0.14 and 0.52+/-0.08, respectively.In these two dioxetane series, the triplet energies of the companion proketones (formaldehyde and fluorenone) to ArCOCH3 are approximately equal to and less than ET1(ArCOCH3).For the 4 and 5 series dioxetanes, there was no change in triplet efficiency with various aryl substituents, where the average αT values are 29.1+/-2.4percent for 4 and 28.1+/- 0.7percent for 5.For these two dioxetane series, the triplet energy of the companion proketone (acetone) is higher than ET1(ArCOCH3).With regard to triplet efficiencies, all of these dioxetane series fall into two categories: (i) where the companion proketones possess triplet energies approximately equal to or less than ET1(ArCOCH3) and where αT is dependent upon substituent changes in the ArCOCH3 moiety; (ii) where the companion proketone possesses a triplet energy higher than ET1(ArCOCH3) and αT is independent of substitution changes in the ArCOCH3 moiety.An exciplex or encounter complex process is proposed to explain the apparent communication between the two proketone moieties in category i dioxetanes.Activation parameters for series 3-5 were typical of most other tetrasubstituted dioxetanes.The ρ values for ?+ correlations of series 3 and 4 plus 5 dioxetanes are -0.285 +/- 0.033 and -0.20 +/- 0.05, respectively, which is consistent with a 1,4-dioxy biradical decomposition process.
