480423-14-1Relevant articles and documents
Sterically Controlled Late-Stage C-H Alkynylation of Arenes
Mondal, Arup,Chen, Hao,Fl?mig, Lea,Wedi, Philipp,Van Gemmeren, Manuel
supporting information, p. 18662 - 18667 (2019/11/28)
Phenylacetylenes are key structural motifs in organic chemistry, which find widespread applications in bioactive molecules, synthetic intermediates, functional materials, and reagents. These molecules are typically prepared from prefunctionalized starting materials, e.g. using the Sonogashira coupling, or using directing group-based C-H activation strategies. While highly efficient, these approaches remain limited by their inherent selectivities for specific regioisomers. Herein we present a complementary approach based on an arene-limited nondirected C-H activation. The reaction is predominantly controlled by steric rather than electronic factors and thereby gives access to a complementary product spectrum with respect to traditional methods. A broad scope as well as the suitability of this protocol for late-stage functionalization are demonstrated.
Cobalt-Catalyzed Cross-Couplings of Bench-Stable Alkynylzinc Pivalates with (Hetero)Aryl and Alkenyl Halides
Hammann, Jeffrey M.,Thomas, Lucie,Chen, Yi-Hung,Haas, Diana,Knochel, Paul
supporting information, p. 3847 - 3850 (2017/07/26)
A catalytic system consisting of CoCl2·2LiCl and TMEDA enables the cross-coupling of various electron-poor aryl and heteroaryl halides with various alkynylzinc pivalates. Coupling with alkenyl halides proceeds with retention of configuration.
Rational Syntheses of Porphyrins Bearing up to Four Different Meso Substituents
Rao, Polisetti Dharma,Dhanalekshmi, Savithri,Littler, Benjamin J.,Lindsey, Jonathan S.
, p. 7323 - 7344 (2007/10/03)
Porphyrins bearing specific patterns of substituents are crucial building blocks in biomimetic and materials chemistry. We have developed methodology that avoids statistical reactions, employs minimal chromatography, and affords up to gram quantities of regioisomerically pure porphyrins bearing predesignated patterns of up to four different meso substituents. The methodology is based upon the availability of multigram quantities of dipyrromethanes. A procedure for the diacylation of dipyrromethanes using EtMgBr and an acid chloride has been refined. A new procedure for the preparation of unsymmetrical diacyl dipyrromethanes has been developed that involves (1) monoacylation with EtMgBr and a pyridyl benzothioate followed by (2) introduction of the second acyl unit upon reaction with EtMgBr and an acid chloride. The scope of these acylation methods has been examined by preparing multigram quantities of diacyl dipyrromethanes bearing a variety of substituents. Reduction of the diacyl dipyrromethane to the corresponding dipyrromethane-dicarbinol is achieved with NaBH4 in methanolic THF. Porphyrin formation involves the acid-catalyzed condensation of a dipyrromethane-dicarbinol and a dipyrromethane followed by oxidation with DDQ. Optimal conditions for the condensation were identified after examining various reaction parameters (solvent, temperature, acid, concentration, time). The conditions identified (2.5 mM reactants in acetonitrile containing 30 mM TFA at room temperature for 3B, trans-A2B2, trans-AB2C, cis-A2B2, cis-A2BC, and ABCD were prepared, including >1-g quantities of three porphyrins.
