The stereochemical course of the high-pressure reaction of 2,5-dialkylfurans with diethyl mesoxalate

Asymmetric Friedel–Crafts reaction of furans with alkyl glyoxylates catalyzed by (salen)Co(II) complexes

“…An improvement in the yield of the reaction was achieved by using the high-pressure technique [7]. It was known from our earlier studies, that this reaction was accelerated by pressure in the absence of Lewis acids [8]. Table 1 shows an effect of pressure on both the yield and the enantioselectivity of this reaction.…”

“…Without a catalyst, this glyoxylate gave a very low asymmetric induction (below 10% d.e.). The non-catalyzed reaction carried out in toluene under the pressure of 10 kbar gives a significant proportion of the byproduct 12 (11:12 ≈ 3:7) (Scheme 3) [8], whereas the addition of the cobalt catalyst 3a favors formation of the Friedel-Crafts product 11. A slightly higher diastereomeric excess of 11 was achieved using the catalyst 3a having (1S,2S) configuration (Scheme 3).…”

“…( -hydroxyacetic acid n-butyl ester (6) 1 H NMR (200 MHz, CDCl 3 ), δ (ppm): 6.23 (d, J = 3.2 Hz, 1H), 5.91 (d,J = 3.2 Hz,1H),5.13 (d,J = 6.7 Hz,1H),2H) -hydroxyacetic acid n-butyl ester (7) 1 H NMR (200 MHz, CDCl 3 ), δ (ppm): 7.34-7.17 (m, 5H), 6.26 (d,J = 3.2 Hz,1H),5.93 (d,J = 3.2 Hz,1H), 5.12 (d,J = 6.6 Hz,1H),2H), 3.94 (s, 2H), 3.3 (d, J = 6.6 Hz), 1.64-1.49 (m, 2H), 1.37-1.18 (m, 2H) -acetic acid n-butyl ester (8) 1 H NMR ( 4.4.10. 2,- [1,3] dioxolane (13) Each one of the esters (S)-11, 4, and 5 was separately reduced with LiAlH 4 in THF at reflux.…”

Catalytic Formal Benzylic C–H Bond Functionalization of 2,5-Dialkylfuran Derivatives with Ferrocenyl Alcohols as Alkylation Reagents

“…To the best of our knowledge, the direct benzylic C–H bond functionalization of 2,5-dialkylfuran under mild conditions still remains elusive to date despite the high significance of 2,5-substituted furan scaffolds in pharmaceutical fields. Very harsh conditions, e.g., high pressure (20 kbar) or strong Lewis acids, were indispensable for effective direct benzylic C–H functionalization, and the electrophiles were considerably limited, which were mainly focused on the highly reactive carbonyl compounds (Scheme , b) . With increasing concerns on environmental protection, identification of the methods without transition-metal catalysts are of considerable significance.…”

Highly Diastereoselective Friedel−Crafts Reaction of Furans with 8-Phenylmenthyl Glyoxylate

“…Such an approach can be performed in two ways: by addition of lithiated furans to the carbonyl group or by the Lewis acid catalyzed Friedel−Crafts reaction. Until now, there was no effective diastereoselective or enantioselective , synthetic method for furan derivatives of type I based on the latter approach. However, there are known examples of efficient diastereoselective and enantioselective ,, Friedel−Crafts reactions of carbonyl compounds with other aromatic derivatives.…”