Rhodium(II)-catalyzed cyclization of 2-alkynyl 2-diazo-3-oxobutanoates as a method for synthesizing substituted furans

Rearrangements of cyclopropenes into five-membered aromatic heterocycles: mechanistic aspect

“…It was eventually discovered that carrying out the reaction between an alkyne and a diazocarbonyl compound in the presence of Rh or Cu catalyst at elevated temperatures allows for direct access to furans in a single step without isolation or even observation of cyclopropene intermediates. Direct preparation of furans via this method was reported by Ma [22], Basak [23], Lee [24], Davies [25], Padwa [26,27,28], and Maas [29]. At the same time, this process is often referred to as a catalytic version of [2+3] dipolar cycloaddition, and some authors even propose alternative mechanistic rationales that do not involve the cyclopropenation step.…”

Computer-Guided Design in Molecular Recognition: Design and Synthesis of a Glucopyranose Receptor

“…Formation of the dienolate of 13 followed by reaction with the bromide 14 , which was prepared in two steps from 2‐butyn‐1,4‐diol,23 gave 15 . Conversion of 15 into the diazo compound by reaction with tosyl azide followed by a rhodium‐catalyzed cyclization gave 16 24. Deprotonation of 16 adjacent to the carbonyl group followed by alkylation of the resulting enolate with 10 resulted in the formation of 17 .…”

Rhodium(II)‐Catalyzed 1,3‐Dipolar Cycloaddition Reactions

“…The synthesis of furofuranones and indenofuranones 35 from a-diazo ketones having pendant alkynes has also been reported (Eq. Other fused heterocyclic systems include furo [3,4-c]furans [120,121] furo [2,3-b]furans [122] as well as thiobenzofurans [123], and benzoxazoles [124] have also been synthesized with this methodology. Other fused heterocyclic systems include furo [3,4-c]furans [120,121] furo [2,3-b]furans [122] as well as thiobenzofurans [123], and benzoxazoles [124] have also been synthesized with this methodology.…”