Direct Synthesis of Chiral Allenoates from the Asymmetric CH Insertion of α‐Diazoesters into Terminal Alkynes

Abstract

The asymmetric C-H insertion of α-diazoesters into 1-alkynes was achieved using chiral cationic guanidinium salts and copper(I) complexes. Optically active 2,4-disubstituted allenoates were generated under mild reaction conditions from various α-diazoesters and 1-alkynes in high yield (up to 99%) and enantioselectivity (up to 97:3 e.r.). Control experiments excluded the possibility of an asymmetric isomerization of alkynoates.

Palladium‐Catalyzed Enantioselective Alkoxycarbonylation of Propargylic Carbonates with (R)‐ or (S)‐3,4,5‐(MeO)3‐MeOBIPHEP

“…High yields and excellent enatioselectivities were obtained in the tandem addition/isomerization process, although in some cases the alkynoate intermediates were detected, which can be further transformed into allenoates under the identical reaction conditions. Asymmetric C−H insertion of α‐diazoesters into terminal alkynes is an alternate method to access chiral trisubstituted allenoates (Scheme h) . Catalyzed by copper(I) complexes and chiral cationic guanidinium salts, enantiomerically enriched allenoates may be produced.…”

“…Asymmetric CÀHi nsertion of a-diazoesters into terminala lkynes is an alternate method to accessc hiral trisubstitutedallenoates (Scheme1h). [13] Catalyzed by copper(I) complexes and chiral cationic guanidinium salts, enantiomerically enriched allenoates may be produced. Apart from these, chiral trisubstituted allenoates may be synthesized from the relatively complicated cyclopropenonylmethyl acetates catalyzed by aL ewis base with good yields and enatioselectivities (Scheme 1i).…”

Cu(I)‐Catalyzed Cross‐Coupling of Diazo Compounds with Terminal Alkynes: An Efficient Access to Allenes

“…Feng, Liu and coworkers made a breakthrough in 2015. They reported the first catalytic asymmetric allene synthesis that involves the coupling between terminal alkynes and α ‐diazoesters in the presences of chiral cationic guanidinium salts/Cu(I) complex (Figure ) . The reaction afforded various di ‐substituted chiral allenoates with high yields and excellent enantioselectivity under mild reaction conditions.…”

(Imidazol‐2‐yl)methyl‐1,3‐propanediones: Regioselective C–H Functionalization of the Imidazole Ring by Acylacetylene/Aldehyde Pairs

“…Examples include the gold-catalyzed annulation of nitroalkynes with indoles, [9] iridium-photocatalyst-promoted decarboxylative alkynylation of carboxylic acids, [10] gold-catalyzed rearrangement of O-propargylic formaldoximes, [11] iron-assisted cycloaddition reaction of diynes with phosphaalkynes, [12] gold-catalyzed cyclization of 2-alkynyl-N-propargylanilines, [13] alkyne oxidation/C-H functionalization under the action of Zn(OTf ) 2 , [14] rhodium-catalyzed cycloadditions of alkynes with cyclopropylideneacetamides, [15] sunlightdriven decarboxylative alkynylation of α-keto acids with bromoacetylenes, [16] copper-initiated trifluoromethylazidation of alkynes, [17] synthesis of chiral allenoates through the asymmetric C-H insertion of α-diazo esters into terminal alkynes with the help of copper compounds, [18] and Pd-catalyzed cross-coupling of terminal alkynes with ene-yne-ketones. Examples include the gold-catalyzed annulation of nitroalkynes with indoles, [9] iridium-photocatalyst-promoted decarboxylative alkynylation of carboxylic acids, [10] gold-catalyzed rearrangement of O-propargylic formaldoximes, [11] iron-assisted cycloaddition reaction of diynes with phosphaalkynes, [12] gold-catalyzed cyclization of 2-alkynyl-N-propargylanilines, [13] alkyne oxidation/C-H functionalization under the action of Zn(OTf ) 2 , [14] rhodium-catalyzed cycloadditions of alkynes with cyclopropylideneacetamides, [15] sunlightdriven decarboxylative alkynylation of α-keto acids with bromoacetylenes, [16] copper-initiated trifluoromethylazidation of alkynes, [17] synthesis of chiral allenoates through the asymmetric C-H insertion of α-diazo esters into terminal alkynes with the help of copper compounds, [18] and Pd-catalyzed cross-coupling of terminal alkynes with ene-yne-ketones.…”