Copper-Catalyzed Intramolecular Hydroalkoxylation of α-(1-Hydroxy-1-alkyl- and -aryl)methylallenoates by a 5-Endo Mode for Preparation of 2-Alkyl- and 2-Aryl-2,5-dihydrofurans

Abstract

Ethyl α-(1-hydroxy-1-alkyl)methylallenoates and α-(1-hydroxy-1-aryl)methylallenoates containing not only electron-donating groups but also an electron-withdrawing group on the aryl group at the α-position have been shown to undergo an efficient and selective copper-catalyzed intramolecular hydroalkoxylation to give functionalized 3-ethoxycarbonyl-2-alkyl- and -aryl-2,5-dihydrofurans in good to excellent yields through a 5-endo mode.

First-Row Late Transition Metals for Catalytic Alkene Hydrofunctionalisation: Recent Advances in C-N, C-O and C-P Bond Formation

“…Intramolecular hydroalkoxylation of α-hydroxymethylallenes is one way to prepare 2,5-dihydrofurans. In 2012, Lee et al, developed a method lying on the use of copper(I) and copper(II) halides as catalysts in the cyclisation of ethyl α-(1-hydroxy-1-alkyl)methylallenoates and α-(1-hydroxy-1-aryl)methylallenoates [ 91 ]. The best conditions are found with CuCl 2 (5 mol %) in DMF at 110 °C ( Scheme 34 ).…”

Regioselectivities in Fe(III)‐catalyzed Cycloisomerization Reactions of γ‐Allenyl Alcohols

“…Among various allenols, extensively investigated reactions was on the α‐allenols to be converted into 2,5‐dihydrofurans under silver catalysis (AgBF 4 or AgNO 3 ) . The regioselectivity favored for 5‐ endo products was also observed in other catalysis using AuCl 3 , LAu(I)X, CuCl 2 , PtCl 2 , and Hg(ClO 4 ) 2 metals, and cyclization of chiral α‐allenols resulted the successful axial‐to‐center chirality transfer 2g–i,4c . A more competitive study was performed with allenyl diols, resulting the cyclization of the more hindered hydroxy group through the allene–metal complexation at the less congested face 2h–k .…”

Base‐Promoted Formation of an Annelated Pyrrolo‐1,4‐oxazine Ensemble from 1H‐pyrrol‐2‐ylmethanol and Propargyl Chloride: A Theoretical and Experimental Study

“…Since pyrrole-2-carbaldehydes and products of their reduction, 2-hydroxymethylpyrroles, are known to be among most readily available α-functionalized pyrroles, [46] and the reaction of alcohols with allenes has been studied in some detail, [47][48][49] it is reasonable to propose the following scheme for the construc- However, our experiments have shown that the reduction of N-allenylpyrrole-carbaldehyde under the standard conditions yields a difficult-to-separate mixture of hardly identifiable products. For this reason, the initial strategy has been changed: first, we intended to carry out propargylation of the previously obtained 2-hydroxymethylpyrrole followed by cyclization of the formed adduct.…”

“…Since pyrrole‐2‐carbaldehydes and products of their reduction, 2‐hydroxymethylpyrroles, are known to be among most readily available α‐functionalized pyrroles, and the reaction of alcohols with allenes has been studied in some detail, it is reasonable to propose the following scheme for the construction of the pyrrolo‐oxazine ensembles: pyrrole‐ N ‐allenylpyrrole‐ N ‐allenylpyrrole‐carbaldehyde‐ N ‐allenyl‐2‐hydroxymethylpyrrole‐pyrrolo[2,1‐c][1,4]oxazine (Scheme ).…”