Pericyclic Reactions

Ruthenium-Catalyzed Chemo-Selective Carbene Insertion into C–H Bond of Styrene over Cyclopropanation: C–C Bond Formation

“…Next, we tested the reaction under lower temperature using reactants 1 and 2 in the presence of ruthenium catalyst and ended up with a mixture of products 3a and 4a instead of a single isomer (Scheme 3b). Then, we carried out the reaction between styrene and H diazo ester (5) under standard reaction conditions, but the reaction did not provide the desired product 6a or 7a, instead of that we ended up with uncharacterized products (Scheme 3c). Further, we checked the product mixture 4a and 5a under basic medium to understand whether the hydrogen migration can be accelerated by base to yield either 4a or 5a; nonetheless, no reaction was observed (Scheme 3d).…”

“…13 C{ 1 H} NMR (100 MHz, CDCl 3 ) δ: 171. 5,167.1,140.0,139.0,138.6,137.8,136.3,133.3,132.9,132.8,132.4,131.6,130.7,130.1,130.1,129.4,128.8,128.7,128.6,128.0,127.5,126.8,126.6,126.5,126.0,61.5,61.2,54.1,36.3,14.3,14.1. IR (KBr) Ethyl 35 (3n/4n).…”

“…13 C{ 1 H} NMR (100 MHz, CDCl 3 ) δ: 172.0, 167. 5,138.7,137.6,137.5,136.6,136.0,135.9,133.7,133.6,132.6,131.7,131.3,129.7,129.3,129.2,128.9,128.5,126.3,125.5,121.7,121.3,61.2,61.0,54.4,35.9,21.1,21.0,14.2,14.1. IR (KBr) Ethyl (E)-4-(4-Chlorophenyl)-2-(p-tolyl)but-3-enoate/Ethyl (Z)-4-(4-Chlorophenyl)-2-(p-tolyl)but-2-enoate (3r/4r).…”

“…In general, there are several methodologies reported in the literature to make a carbon−carbon bond using transition metal catalysts. Several classical examples, such as Friedel−Crafts reactions, 1 Wittig reactions, 2 cross-coupling reactions, 3 C−H activation and functionalization, 4 pericyclic reactions, 5 domino reactions, 6 organometallic reagents and numerous other C−C bond forming reactions 7 are very useful methodologies. Moreover, cross-coupling reactions and other related reactions have emerged as an important and powerful tool to achieve C−C bond formation in the synthesis of various natural products and potential drugs.…”