Chemoselective Transformations of Cyclic β-Bromoacrylic Acids with Palladacycles Formed by Aryl Iodides to Access Fused or Spiro Polycycles

Abstract

A palladium-catalyzed chemoselective decarboxylative annulation of different aryl iodides with cyclic β-bromoacrylic acids for the construction of interesting fused and spiro polycycles is disclosed. Notably, cyclic β-bromoacrylic acids can chemoselectively act as C1 or C2 insertion units by the use of different aryl iodides. 2-Iodo-N-methacryloylbenzamides can undergo a Heck/[4+2] annulation to afford hexahydrodibenzoisoquinoline-4,6(5H)-diones. Employing 2-iodobiphenyls or N-(2-iodophenyl)-2-phenylacrylamides as substrates enables the assembly of spirofluorenes and dispirooxindoles.

Decarboxylative cyclization of o-chlorobenzoic acids with C,C-palladacycles formed by an aminopalladation/dealkylation strategy to access dibenzo[a,c]carbazoles

“…On the basis of the above experimental results and previous work, 10–14,18 we propose a plausible mechanism for this protocol (Scheme 3). First, arylpalladium( ii ) species A is generated by oxidative addition of the C–Br bond in 1a to Pd(0), which is subsequently converted into intermediate B via an intramolecular aminopalladation by the coordination of Pd( ii ) to alkyne.…”

“…1 In the past few decades, five-membered C , C -palladacycle-based reactions have attracted widespread attention due to their versatile conversions in which two C–Pd bonds could be functionalized by trapping with coupling reagents. 2–16 Among them, of extraordinary interest to synthetic chemists are cyclizations of five-membered C , C -palladacycles with various coupling reagents such as aryl halides, 3 arynes, 4 alkynes, 5 diaziridinones, 6 diazo compounds, 7 bromophenols, 8 dibromomethane, 9 halogenated carboxylic acids, 10–14 etc ., which have emerged as a powerful tool for the construction of polycyclic compounds. Recently, the groups of Kwong, us and others achieved the transformation of five-membered C , C -palladacycles by various halogenated carboxylic acids via a carboxyl-assisted palladacycle capture strategy, leading to the construction of diverse fused polycycles (Scheme 1a).…”

“…Recently, the groups of Kwong, us and others achieved the transformation of five-membered C , C -palladacycles by various halogenated carboxylic acids via a carboxyl-assisted palladacycle capture strategy, leading to the construction of diverse fused polycycles (Scheme 1a). 10–14 Despite great progress, there are still some limitations in this field: (1) a C–H activation process was required to form C , C -palladacycles. (2) These methods were restricted to the construction of C–C bonds.…”

“…17 Very recently, Shi and co-workers reported the synthesis of indolo[3,2- b ]indoles and indeno[1,2- b ]indoles from o -alkynylanilines with diaziridinone or α-diazo esters, in which a C , C -palladacycle was formed by a aminopalladation/dealkylation strategy. 18 Inspired by these advances and our ongoing interest in transformations of C , C -palladacycles, 11,13,16 we herein disclose a decarboxylative biscyclization cascade of o -chlorobenzoic acids with o -alkynylanilines (Scheme 1b). Notably, this reaction enables the construction of one C–N bond and two C–C bonds via C , C -palladacycles generated by the aminopalladation/dealkylation strategy, thus furnishing dibenzo[ a , c ]carbazoles, which are ubiquitous privileged frameworks in natural products, pharmaceuticals, and functional materials.…”

Research advances in palladium-catalysed intermolecular C–H annulation of aryl halides with various aromatic ring precursors

“…Subsequently, our group and others designed various halogenated carboxylic acids as C1, C2 or C3 insertion units to construct different size-ring fused cyclic compounds via this strategy. [53][54][55][56][57][58][59][60][61][62] In these reactions, it was observed that the inser- tion of carboxylic acids usually showed good regioselectivity. Thus, the methods used o-halobenzoic acids, arynes and aryl halides as aromatic ring precursors, which could be complementary.…”