Reaction of 2-Imino-2,5-dihydrofuran-3-carboxamides with Benzaldehyde
- PDF / 194,968 Bytes
- 3 Pages / 612 x 792 pts (letter) Page_size
- 94 Downloads / 147 Views
T COMMUNICATIONS
Reaction of 2-Imino-2,5-dihydrofuran-3-carboxamides with Benzaldehyde L. V. Karapetyana,* and G. G. Tokmajyana a
Yerevan State University, Yerevan, 0025 Armenia *e-mail: [email protected]
Received June 29, 2020; revised July 12, 2020; accepted July 18, 2020
Abstract—The reaction of 2-imino-2,5-dihydrofuran-3-carboxamides with benzaldehyde in pentan-1-ol in the presence of piperidine gave new dihydrofuran derivatives with a fused pyrimidine ring and two phenyl rings, 2-phenyl-5-(2-phenylethylidene)-5,6-dihydrofuro[2,3-d]pyrimidin-4(3H)-ones. The product structure was confirmed by spectroscopic methods (1H and 13C NMR) and independent synthesis from previously reported 2-imino-5,5-dimethyl-4-(2-phenylethenyl)-2,5-dihydrofuran-3-carboxamide and benzaldehyde under similar conditions. Keywords: 2-imino-2,5-dihydrofuran-3-carboxamide, benzaldehyde, 2-phenyl-5-(2-phenylethylidene)-5,6-dihydrofuro[2,3-d]pyrimidin-4(3H)-one
DOI: 10.1134/S1070428020100280 Both natural and synthetic compounds containing a 2-oxo- or 2-imino-2,5-dihydrofuran ring possess a wide range of practically important properties, the most valuable of which is their diverse biological activity such as antibacterial, antibiotic, antiviral, carcinolytic, etc. [1, 2].
The reactions of 1a–1c with benzaldehyde (2) were carried out by heating the reactants at a ratio of 1:2 in boiling pentan-1-ol in the presence of piperidine for 30 min. As a result, we isolated compounds containing two phenyl rings and a fused pyrimidine ring, 2-phenyl-5-(2-phenylethylidene)-5,6-dihydrofuro[2,3-d]pyrimidin-4(3H)-ones 3a–3c (Scheme 1). This reaction pathway was expected since both 4-methyl group conjugated with the C=C double bond and C=NH moiety are active centers in molecules 1a–1c. Similar reactions in the iminocoumarin series were reported previously [7].
It is known that the methyl group in 2-oxo- and 2-imino-4-methyl-2,5-dihydrofurans is activated due to conjugation with the C=C double bond and is capable of reacting with aldehydes [3–5]. In continuation of our studies in the field of synthesis of new iminodihydrofuran derivatives, herein we report the reaction of 5,5-dialkyl-2-imino-4-methyl-2,5-dihydrofuran-3-carboxamides 1a–1c [6] with benzaldehyde. Compounds 1a–1c are polyfunctional unsaturated γ-imino lactones, so that different reaction directions are possible.
The structure of 3a–3c was confirmed by 1H and 13 C NMR spectra and elemental analyses. The 1H NMR spectra of 3a–3c showed signals at δ 3.60 and 6.25 ppm for protons of the CH2 and CH groups, and
Scheme 1. O Me R
NH2 +
1
R
2
O
PhCHO
Piperidine reflux, 30 min
NH R
NH 2
=
1
R
1a–1c
R1
O
Ph
R2
= Me (a),
2
O 3a–3c
R1
= Me,
R2
= Et (b),
1844
R1R2
= (CH2)5 (c).
N
Ph
1845
REACTION OF 2-IMINO-2,5-DIHYDROFURAN-3-CARBOXAMIDES Scheme 2. O
Ph
NH2 + Me Me
O 4a
PhCHO
Piperidine reflux, 20 min
O
Ph
NH Me
NH
Me 2
aromatic protons resonated in the region δ 8.20– 8.28 ppm. The CH 2 and CH carbon signals were located at δC 33.60 and 116.95 ppm, respectively, in
Data Loading...
