The regioselective Larock indole synthesis catalyzed by NHC–palladium complexes

An Oxidant- and Catalyst-Free Synthesis of Dibenzo[a,c]carbazoles via UV Light Irradiation of 2,3-Diphenyl-1H-indoles

“…. 33 Compound 1b was purified by column chromatography on silica gel (EA/PE 1:30 to 1:10). yellow oil.…”

“…1 H NMR (600 MHz, CDCl 3 ):  = 7.86 (dd, J = 12.9, 7.9 Hz, 2 H), 7.51-7.42 (m, 2 H), 7.37-7.32 (m, 4 H), 7.25 (s, 1 H), 4.24 (s, 2 H), 2.77 (s, 3 H). 13 32,33 Typical Procedure B A mixture of 2-phenyl-1-(p-tolyl)ethan-1-one (3b; 210.0 mg, 1.0 mmol, 1.0 equiv) and phenylhydrazine (108.0 mg, 1.0 mmol, 1.0 equiv) was dissolved in EtOH (15 mL). Then, concentrated sulfuric acid (196.0 mg, 2.0 mmol, 2.0 equiv) was slowly added to the reaction mixture and the resulting solution was refluxed at 90 °C.…”

Palladium(II)/N‐Heterocyclic Carbene‐Catalyzed Regioselective Heteroannulation of Tertiary Propargyl Alcohols and o‐Haloanilines to form 2‐Alkenylindoles

“…In addition, installation of wide range of substitutents at the nitrogen atoms of NHCs manifests asymmetric, steric, chelating and π–π stacking features . Reports on metal‐NHC catalysts in Larock heteroannulation are scarce . Our group has previously reported the Ru(II)‐catalyzed regioselective deoxygenation–oxidative annulation of propargyl alcohols with phthalazinones and pyridazinones .…”

Synthesis of 2-BMIDA indoles via heteroannulation: Applications in drug scaffold and natural product synthesis

“…Ultimately this required the use of N-acyl 2-iodoaniline (1b) under the more classical Larock conditions for this aryl-substituted alkyne, giving 4 in good yield (entry 6). The origin of this difference in reactivity is uncertain but the increased steric bulk of alkyne 2b is very likely to dominate, [7][8][9][17][18][19] with electronic effects also a minor contributor. 20,21 These conditions were subsequently assessed for generality across a series of annulations (Scheme 2).…”

“…Aryl-and alkenyl-substituted alkynes were also broadly compatible with the annulation, giving a similar series of products; however, a general lower efficiency was noted for arylsubstituted alkynes, consistent with previous observations with bulky alkynes in this area. [7][8][9][17][18][19] Scheme 2. Example scope of the annulation process.…”