77037-49-1Relevant articles and documents
Cp?Ir(III)-Catalyzed C-H/O-H Functionalization of Salicylaldehydes for the Synthesis of Chromones at Room Temperature
Lade, Dhanaji M.,Aher, Yogesh N.,Pawar, Amit B.
, p. 9188 - 9195 (2019/08/12)
Herein, we report Cp Ir(III)-catalyzed C-H/O-H-bond functionalization of salicylaldehydes with α-diazocarbonyl compounds for the synthesis of chromones under redox-neutral conditions. The reaction proceeds at room temperature and displays excellent functi
Controllable Rh(III)-Catalyzed Annulation between Salicylaldehydes and Diazo Compounds: Divergent Synthesis of Chromones and Benzofurans
Sun, Peng,Gao, Shang,Yang, Chi,Guo, Songjin,Lin, Aijun,Yao, Hequan
, p. 6464 - 6467 (2016/12/23)
A Rh(III)-catalyzed annulation between salicylaldehydes and diazo compounds with controllable chemoselectivity is described. AgNTf2 favored benzofurans via a tandem C-H activation/decarbonylation/annulation process, while AcOH led to chromones through a C-H activation/annulation pathway. The reaction exhibited good functional group tolerance and scalability. Moreover, only a single regioisomer of benzofuran was obtained due to the in situ decarbonylation orientation effect.
Kinetic and Thermodynamic Control in the Lithiation of 2,6-Dimethylchromone, and Selective Lithiations in 2-(x-Furyl)chromones and in Furanochromones Related to Khellin
Costa, Anna M. B. S. R. C. S.,Dean, Francis M.,Jones, Michael A.,Smith, Dennis A.
, p. 1707 - 1712 (2007/10/02)
The addition of 2,6-dimethylchromone to lithium di-isopropylamide (LDA) allows formation, under thermodynamic control, of the 2-methylene carbanion (3), but this seems to react at the carbonyl oxygen atom with carbon dioxide so no caboxylic acid can be isolated.With ethyl chloroformate (but not diethyl carbonate) this carbanion does afford the expected ethyl chromon-2-ylacetate (1d).The chromonylacetic acid is also obtainable if the starting chromone bears a free hydroxy group at position 5 as in (4a).From the addition of 2,6-dimethylchromone to a mixture of LDA and diethyl carbonate there results ethyl 2,6-dimethylchromone-3-carboxylate (9b) because the chromone 3-carbanion formed under kinetic control is trapped before it isomerises.The reaction resembles that found in flavones.Flavone (at the 3-position) and furan or benzofuran (at the 2-position) are about equally effective in competing for deprotonation by LDA.Khellin (14a) is probably deprotonated by LDA at both furan and pyrone sites but carboxylation affords only the furan carboxylic acid (14b) and unchanged khellin.This accords with the above results, as does the deprotonation and carboxylation of the phenol (15b), norvisnagin, which affords the chromonylacetic acid (16).With LDA followed by carbon dioxide the 2-(2-furyl)chromone (18a) surprisingly gives only the dicarboxylic acid (18b); apparently the dicarbanion is more stable than either monocarbanion.The isomeric 2-(3-furyl)chromone (20a) under similar conditions affords only the chromone-3-carboxylic acid (20b); the furan ring is untouched.
β-Deprotonation by Lithium Di-isopropylamide. Vinyl Carbanions from Oxygen Heterocycles in the Synthesis of Carboxylic Acids in the Benzofuran, Flavone, and Coumarin Series and in the Regiospecific Acylation of 2,6-Dimethylchromone
Costa, Ana M. B. S. R. C. S.,Dean, Francis M.,Jones, Michael A.,Smith, Dennis A.,Varma, Rajender S.
, p. 1224 - 1226 (2007/10/02)
Lithium di-isopropylamide at -70 deg C can remove the α-proton from benzofuran in the absence of activating groups and the β-proton if such groups are present; in flavone and 4-methoxycoumarin β-deprotonation occurs readily and the carbanions are easily carboxylated giving acids not previously accessible, while in 2,6-dimethylchromone β-deprotonation is kinetically favoured allowing 3-acylation to be achieved separately from the conventional acylation at the 2-methyl group.
