Annulation of Hydrazones and Alkynes via Rhodium(III)-Catalyzed Dual C–H Activation: Synthesis of Pyrrolopyridazines and Azolopyridazines

Abstract

Hydrazones readily synthesized from N-aminopyrroles or N-aminoazoles and aldehydes undergo Rh(III)-catalyzed dual C−H activation and coupling with aryl and alkyl substituted alkynes to give pyrrolopyridazines or azolopyridazines, respectively. This transformation represents a rare example of hydrazoyl C−H activation and proceeds without heteroatom functionality to direct C −H activation. Hydrazones derived from aromatic, alkenyl, and aliphatic aldehydes were effective inputs, and tethering the alkyne to the hydrazone enabled annulations to more complex, tricyclic products.

Synthesis of the Novel N-(2-Hexadecynoyl)-l-Homoserine Lactone and Evaluation of Its Antiquorum Sensing Activity in Chromobacterium violaceum

“…Alcohol 3b (0.5 g, 3.1 mmol) was obtained as a colorless oil in a 73% yield. The spectroscopic data gathered for 3b are in complete agreement with the spectroscopic data reported in the literature for this compound. − …”

“…The solvent of the filtered solution was removed in vacuo. The obtained yellowish liquid was purified using silica gel column chromatography, eluting the 6-decynoic (16), 135 (8), 122 (26), 108 (46), 93 (50), 79 (100), 67 (43), 59 (19), 55 (19).…”

The Application of Microwaves, Ultrasounds, and Their Combination in the Synthesis of Nitrogen-Containing Bicyclic Heterocycles

“…For the compounds 82 and 83, the yields were 90% and 91%, respectively, in comparison to 70% for the conventional heating. In a recent paper, the synthesis of many nitrogen heterocycles obtained using a Rh(III)-catalyzed imidoyl C-H functionalization was reported [124]. The use of a Rh (III) catalyst and microwave heating allowed for the efficient preparation of pyrrolopyridazines 84 as reported in Scheme 66.…”

Dual C–H activation: Rh(iii)-catalyzed cascade π-extended annulation of 2-arylindole with benzoquinone

“…On the other hand, although the above-mentioned great breakthrough obtained in C–H functionalization, there are few examples reported for dual C–H activation reactions. 8 During our research program exploring transition-metal catalysis and heterocyclic synthesis, 9 we intended to prepare the indole-containing heterocycles based on the consideration of their potential biological activity. Herein, we report a rhodium-catalyzed N–H free indole directed annulation reaction with BQ through dual C–H activation strategy ( Scheme 1b ).…”