Synthesis and reactions of β-substituted derivatives of furan

Abstract

The 1,4-cycloaddition reaction of 4-phenyl-1,3-oxazole to 2-propinyl benzoate and dimethyl butinedioate afforded the respective 3-furylmethyl benzoate (I) and 3,4-bis(methoxycarbonyl)furan (II). These compounds served for the synthesis of 3-chloromethylfuran and 3,4-bis(chloromethyl)furan, which afforded via Wittig reaction 3-(β-arylvinyl)furans III (aryl = 5-nitro-2-furyl (IIIa), 5-nitro-2-thienyl (IIIb), 1-methyl-4-nitro-2-pyrrolyl (IIIc), and 4-nitrophenyl (IIIe)) and 3,4-bis(β-arylvinyl)furans IV (aryl = 5-nitrofuryl (IVa), 5-nitro-2-thienyl (IVc), and 4-nitrophenyl (IVd)). According to spectral evidence (1H NMR, IR, UV spectra), compound IIIa and IIIb originated as E isomers, whilst the remaining products are a mixture of E and Z isomers; some couples were succeded to separate.

Total synthesis of monosporascone and dihydromonosporascone

“…Low temperature addition 13 of the lithium acetylide generated from ethyl propiolate (27) to 3,5-dimethoxybenzaldehyde (28) gave the expected secondary alcohol 29, which underwent a domino Diels-Alder-retro-Diels-Alder reaction 13,23 with 4-phenyloxazole (30) 24 providing the 3,4-disubstituted furan 31. Lewis or Brønsted acid-catalysed Friedel-Crafts ring closure at this juncture could, in principle, provide access to monosporascone (4) via racemic monosporascol A (6) (Scheme 1); however, we expected the benzylic alcohol to be incompatible with such conditions, and as such this was not attempted.…”

“…R f (EtOAc-hexanes 1 : 9) 0.30; IR ν max cm -1 : 1721 (OCvO), 1672 (CvO). 1 H NMR (500 MHz, CDCl 3 ) δ 7.08 (d, J 2′/6′,4′ = 2.5 Hz, 2H, H2′/6′), 6.84 (d, J 3,2 = 12 Hz, 1H, vinylic), 6.66 (t, J 4′,2′/6′ = 2.5 Hz, 1H, H4′), 6.25 (d, J 2,3 = 12 Hz, 1H, vinylic), 4.07 (q, J = 7 Hz, 2H, OCH 2 ), 3.82 (s, 6H, 2 × OCH 3 ), 1.11 (t, J = 7 Hz, 3H, CH 3 ); 13 C NMR (125.8 MHz, CDCl 3 ) δ 193.9 (CvO), 164.9 (CO 2 ), 161.1 (C3′/5′), 141.1 (vinylic), 137.9 (C1′), 126.3 (vinylic), 106.6 (C2′/6′), 106.3 (C4′), 61.3 (OCH 2 ), 55.7 (OCH 3 ), 13.9 (CH 3 ); MS (EI) m/z 264 (M •+ , 38%), 191 (100), 137 (23), 122 (30) SOCl 2 (500 μL) was added to 38 (36 mg, 0.13 mmol) at 0 °C under argon. The acid dissolved slowly (over 5 h) producing a pale yellow solution.…”