Efficient asymmetric synthesis of spiro-2(3H)-furanones via phase-transfer-catalyzed alkynylation

Abstract

Efficient asymmetric synthesis of spiro-2(3H)-furanones was achieved via phase-transfer-catalyzed highly enantioselective alkynylation of cyclic β-keto esters with hypervalent iodine reagents.

Cyclic Hypervalent Iodine Reagents for Atom‐Transfer Reactions: Beyond Trifluoromethylation

“…[74d] In 2014, Maruoka and co-workers reported the first alkynylation of ketoesters that proceeded with more than 90 % ee (Scheme 35). [75] Key for success with phase-transfer catalyst 151 was the use of phenylbenziodoxole 157 instead of TMS-EBX (81).…”

“…[75] Key for success with phase-transfer catalyst 151 was the use of phenylbenziodoxole 157 instead of TMS-EBX (81). The scope of nucleophiles in the alkynylation reaction was further extended by Vesely and co-workers.…”

Ultrasonic Aptitude of Regioselective Reaction of 6‐bromo‐spiro‐3,1‐benzoxazinone2,1′‐isobenzofuran‐3′,4‐dione Towards Some Electrophilic and Nucleophilic Reagents

“…The main challenge that arises is to ensure stereo‐control in the C–C bond forming step with a suitable asymmetric catalyst. It is nowadays well accepted that due to the higher basicity of the hydrazine hydrate and 2‐pinacolyl amine that enhanced the nucleophilicity of the carboxylic group of 2‐benzoxazinonylbenzoic acid and increase percentage of the spiro isomer to create the stereogenic center . However, the hereby formed primary addition product is a neutral species and therefore it is difficult to control the subsequent stereo‐defining transformation with those asymmetric electrophilic and nucleophilic reagents that are commonly used to control the subsequent rearrangement .…”

Asymmetric Alkynylation of β‐Ketoesters and Naphthols Promoted by New Chiral Biphenylic Iodanes

“…Other related approaches to asymmetric α‐cyanation or α‐alkynylation of β‐ketoesters are based on the use of achiral λ 3 ‐iodanes of the benziodoxol(on)e type in the presence of a chiral organocatalyst . For example, alkynylations were reported to occur with good to excellent enantioselectivities using Waser's TMS‐EBX λ 3 ‐iodane, or its analogue C , and Maruoka's catalyst B (Scheme ) –…”