Three-component synthesis of functionalized 5-oxo-4,5-dihydroindeno[1,2-b]pyrans

Abstract

Protonation of the reactive intermediates produced in the reaction between alkyl(aryl) isocyanides and dialkyl acetylenedicarboxylates by indan-1,3-dione leads to vinylnitrilium cations, which undergo carbon centered Michael type addition with the conjugate base of the CH-acid to produce functionalized 5-oxo-4,5-dihydroindeno[1,2-b]pyrans.

Facile One-Pot Green Synthesis of Some New Annulated Polyfunctionalised 2-Amino-4H-Pyrans

“…The NH proton in 4a showed spin-spin coupling with the diastereotopic methylene protons and appeared as a doublet of doublets (J 1 = 7.3 Hz, J 2 = 5.8 Hz, δ = 8.90 ppm). The 1 H decoupled 13 C NMR spectrum of 4a showed 21 distinct resonances in agreement with the proposed structure. The mass spectra of 4a displayed M+1 ion peak at 478 m/z values and initial fragmentation involved the loss of ester moieties.…”

“…The reaction of TosMIC 1 with electron-deficient actylenic esters 2 in the presence of cyclic 1,3-dicarbonyl compounds 3 at ambient temperature in PEG-300 leads to the corresponding highly functionalised fused 2-amino-4H-pyrans 4 in good yields (Scheme 1). The structures of compounds 4a-h were determined on the basis of their elemental analyses, mass spectra, 1 H and 13 C NMR and IR spectroscopic data. The 1 H NMR spectrum of 4a exhibited six sharp singlets, readily recognisable as arising from the methyl (δ = 1.03, 1.07, and 2.41 ppm), methoxy (δ = 3.62 and 3.71 ppm), and methine (δ = 4.45 ppm) protons.…”

“…Although the mechanistic details of the above reaction are unknown, a proposed mechanism for this reaction is outlined in Scheme 3 based on the previous reports. [13][14][15][16][17] Initially, the Scheme 2 Scheme 3 for 1 H and 62.9 MHz for 13 C) with CDCl 3 as solvent. Chemical shifts are given in ppm (δ) relative to internal TMS, and coupling constant (J) are reported in Hertz (Hz).…”

“…The reaction mixture was then allowed to warm up to room temperature and stand for 1 h. After completion, the mixture was diluted with water (4 mL) and the product was filtrated and purified by ethyl acetate. 13 …”

“…E-mail: nasiri@uma.ac.ir solvents and usually the time of the reactions was long. [13][14][15][16][17] In continuation of our interest in the generation and trapping of various zwitterionic species by H-acids, [18][19][20] we wish to report the one-pot reaction between cyclic 1,3-dicarbonyl compounds and dialkyl acetylene dicarboxylates in the presence of TosMIC in PEG to produce new highly functionalised 2-amino-4Hpyrans in good to high yields.…”