An oxidative annulation of 2-arylindazoles with cyclic enoneshas was developed using Rh(III)/Cu(OAc) 2 catalytic system for the first time to produce 3,4-dihydroindazolo[2,3-f] phenanthridin-1(2H)-one derivatives in good yields with high selectivity. When AgSbF 6 was used instead of Cu(OAc) 2 , the corresponding uncyclized products, 3-(2-(2H-indazol-2-yl) phenyl)cyclohexan-1-one scaffolds were formed exclusively. The reaction proceeds through a sequential conjugate addition of ortho-C-H bond of aryl group followed by an oxidative annulation of indazole ring to generate fused polycyclic scaffolds.
A novel protocol is accomplished for transformation of 2amino-7,7-dimethyl-5-oxo-4-phenyl-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile (1) into dihydrobenzofuran-2,2-dicarbonitriles (2) by reacting with N-chlorosuccinimide in presence of base at ambient temperature. On the other hand, same reaction with6-amino-3-methyl-1,4-diphenyl-1,4-dihydropyrano [2,3-c]pyrazole-5-carbonitrile (3) and NCS, surprisingly lead to formation of bispyrazolospirocyclopropanes (5). Simple reaction conditions, excellent yields and high compatibility are the advantages of this protocol.Reaction Conditions: 3(1.0 mmol),NaOH(1.0 mmol),NCS (1.0 mmol), water, ambient temperature. [b] Isolated yield and reaction time. Scheme 7. plausible mechanism for compound 2&5.
A novel synthetic protocol for functionalized imidazo[1,2‐a]pyridines were accomplished in one pot by reacting 2‐amino pyridines and propargylic alcohols promoted by lewis acid catalyst. The protocol presented herein, proceeds via Meyer‐Schuster type of rearrangement leading to in situ generation of electron deficient allene and subsequent nucleophilic attack of amines followed by intramolecular cyclization in [3+2] cycloaddition fashion leading to title compounds. Simple reaction conditions, excellent yields and high compatibility are the advantages of this protocol.
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