Novel method for synthesis of aryl hydrazones from α-diazo esters: scope and limitations of nucleophiles

New 2-aryl-6-methyl-3,4-dihydro-β-carbolin-2-iums as potential antifungal agents: Synthesis, bioactivity and structure-activity relationship

“…2. The key intermediates 5a – 5d were synthesized via 6 steps from commercially available 2-arylhydrazin-1-ium chlorides and α-ketoglutaric acid 20 . Target compounds 6- n were obtained by reaction of 5a – 5d and primary aromatic amines in ethanol by using p -toluenesulfonic acid as catalyst in 35‒99% yields.…”

“…Except 6–34 19,20 and 7 21 , all the target compounds are new compounds and their structures were structurally characterized by spectrometric methods including 1 H NMR, 13 C NMR, and MS. All compounds 6 displayed some similar spectroscopic features because of the same molecular skeleton. In 1 H spectra, all the compounds revealed one singlet signals of H-1 in the range of δ H 9.38 to 9.72 ppm, one singlet signal of (N)CH 3 at δ H ca.…”

Visible Light‐Induced [3+2] Cyclization Reactions of Hydrazones with Hypervalent Iodine Diazo Reagents for the Synthesis of 1‐Amino‐1,2,3‐Triazoles

“…The diazomethyl radical can act as carbyne equivalent to construct a chiral carbon center via an assembly point functionalization. Inspired by these results, and as part of our ongoing research on hydrazones [7] and diazo compounds, [5b–d, 8] we proposed that 1‐amino‐1,2,3‐triazoles could be constructed by reacting hydrazones with hypervalent iodine diazo reagents using an aminyl radical‐polar crossover strategy [9]…”

Fischer Indole Synthesis with Organozinc Reagents

“…[7] Since organozinc reagents are readily available, inexpensive, and compatible with numerous functional groups, [9] we envisioned a new retrosynthetic pathway for the Fischer indole synthesis, in which the key intermediates 4 A and 4 B would not be obtained from 2 and 3, but rather from the reaction of readily available aryldiazonium salts of type 5 and functionalized alkylzinc reagents of type 6 (Scheme 1). [10,11] This approach proved to be very fruitful, since many functional groups such as ester, cyano, nitro, and keto groups are tolerated, and unexpectedly the issue of regioselectivity mentioned above is resolved. Thus, the reaction of ethyl 4-bromobutanoate (7 a, 1.1 equiv) with zinc dust (2 equiv), ZnBr 2 (2 equiv), [12] and LiCl (1.1 equiv) in THF produces the expected alkylzinc halide 6 a in 90 % yield (50 8C, 1 h).…”