Ruthenium-Catalyzed Synthesis of cis-2,3-Dihydrobenzofuran-3-ols by Aqueous Transfer Hydrogenation via Dynamic Kinetic Resolution

Abstract

The preparation of cis-2,3-dihydrobenzofuranols with two stereocenters through aqueous asymmetric transfer hydrogenation (ATH) of benzofuranones with the metal catalyst Ru­(II) via dynamic kinetic resolution (DKR) has been developed. A variety of α-alkyl benzofuranones were transformed to obtain optically pure 2,3-dihydrobenzofuran-3-ols with excellent enantioselectivities and acceptable yields under mild conditions.

Escaping from Flatland: Stereoconvergent Synthesis of Three‐Dimensional Scaffolds via Ruthenium(II)‐Catalyzed Noyori–Ikariya Transfer Hydrogenation

“…If the reaction was run for 30 min, the tertiary alcohols could be isolated (Q=OH, Figure 12), and longer reaction times provided, after Pd/C‐catalyzed hydrogenation, the corresponding alkyl or benzyl substituted substrates 43 . These were converted via DKR–ATH to the corresponding cis ‐products 44 with moderate to good yields and enantioselectivities [25] . Additionally, for 4‐, 5‐, or 6‐acetyl‐benzofuran‐3‐ones, a reduction of both ketones (cyclic and acetyl) was achieved, generating a single enantiomer of compounds with three transannular stereocenters, for example 45 [26] …”

Microwave-Assisted Synthesis of Benzofuran-3(2H)-ones

“…The solutions were subsequently examined. Cosolvent systems seemed to be better than single solvents (Table 1, entries [1][2][3][4][5][6][7][8]. Among the catalysts investigated, K 3 PO 4 , CH 3 CO 2 K, and Cs 2 CO 3 were more efficient during these common alkaline salts ( Table 1, entries 19-31).…”

“…4 This is a quick and facile method for organic synthesis, often giving higher product yields and allowing for easier isolation. 5 However, microwave synthesis of Previous work: 8 Our work: benzofuranones has seldom been reported. 6 We have adopted the microwave-assisted synthesis to obtain the desired benzofuranones for our study on chiral dihydrobenzofuranones.…”

Recent Progress and Applications of Transition-Metal-Catalyzed Asymmetric Hydrogenation and Transfer Hydrogenation of Ketones and Imines through Dynamic Kinetic Resolution

“…In 2017, Fang and co-workers reported the Ru-catalyzed synthesis of cis-2,3-dihydrobenzofuran-3-ols by aqueous transfer hydrogenation via DKR by using complex (R,R)-CAT13, HCO 2 Na as a hydrogen source, and CTAB as a phasetransfer catalyst in a CH 2 Cl 2 /H 2 O (1:1) mixture at room temperature (Scheme 23). 36 A variety of 2-alkylbenzofuran-3(2H)-ones were thus converted under mild conditions into cis-2-alkyl-2,3-dihydrobenzofuran-3-ols with 97:3 to >99:1 dr and 80 to >99% ee.…”