Fe-Catalyzed Selective Formal Insertion of Diazo Compounds into C(sp)–C(sp³) Bonds of Propargyl Alcohols: Access to Alkyne-Substituted All-Carbon Quaternary Centers

Abstract

The construction of all-carbon quaternary centers, especially those containing an alkyne-substituted framework, represents an important challenge in organic synthesis. Here we present a novel Fe-catalyzed selective formal insertion of diazo compounds into C(sp)−C(sp 3 ) bonds of propargyl alcohols under mild conditions that enables the streamlined construction of alkynesubstituted all-carbon quaternary centers. This unique strategy starts with in situ generation of an ester group in the presence of carboxylic acids, followed by insertion of metal-carbene into C(sp)− C(sp 3 ) bonds, which may open up a new reaction mode for exploring metal-carbene insertion into acyclic C−C bonds.

Photo-induced spirocyclization of biaryl ynones with ammonium thiocyanate: access to thiocyanate-featured spiro[5,5]trienones

“…According to the experimental results as well as previous studies, 20 a plausible reaction pathway was described as shown in Scheme 5. First, with the assistance of fluorescein/blue light/oxygen, NH 4 SCN could smoothly produce the SCN radical.…”

Ultrasound-promoted synthesis of a copper–iron-based catalyst for the microwave-assisted acyloxylation of 1,4-dioxane and cyclohexene

“…The activation of C-H bonds is an effervescent area of work in organic synthesis. [1][2][3][4][5][6][7] The stringent demands that the current concerns on sustainability pose on the chemical industry require the seeking of new methods for the preparation of high-value commodities. [8][9][10] In this scenario, the development of new catalysts that enables the introduction of oxygenated functions into C(sp 3 )-H bonds is a challenge undertaken by many research groups.…”

Rh(II)-Catalyzed Chemoselective Oxy-alkynylation of Acceptor–Acceptor Carbenes: Synthesis of C2-Quaternary Alkyne-Substituted 3(2H)-Furanones

“…Transition-metal carbenes obtained from diazo compounds have been extensively used in organic synthesis. − They can react with various functional groups. Among them, alkynes show a particularly diverse pattern of reactivity .…”

“…Compared to the well-developed cyclopropenations, the alkynylations involving carbenes for the construction of alkyne-substituted quaternary centers are still underdeveloped (Scheme A, right) . In spite of this, great achievements have been made in the past few decades (Scheme B). − , For example, Liang and co-workers described a specific protocol for the synthesis of 1,5-enynes bearing all-carbon quaternary centers via a palladium(0)-catalyzed decarboxylation of allyl 3-arylpropiolates and subsequent insertion of aryldiazoacetates (Scheme B, a) . Recently, a selective Fe-catalyzed formal insertion of diazo compounds into C­(sp)–C­(sp 3 ) bonds of propargyl alcohols in the presence of carboxylic acids was established, which can provide an alternative route to alkyne-substituted all-carbon quaternary centers (Scheme B, b) .…”

“…In spite of this, great achievements have been made in the past few decades (Scheme B). − , For example, Liang and co-workers described a specific protocol for the synthesis of 1,5-enynes bearing all-carbon quaternary centers via a palladium(0)-catalyzed decarboxylation of allyl 3-arylpropiolates and subsequent insertion of aryldiazoacetates (Scheme B, a) . Recently, a selective Fe-catalyzed formal insertion of diazo compounds into C­(sp)–C­(sp 3 ) bonds of propargyl alcohols in the presence of carboxylic acids was established, which can provide an alternative route to alkyne-substituted all-carbon quaternary centers (Scheme B, b) . Despite these successes in the insertion of diazo-derived metal carbenes into the C–C bond of alkynes, , more diverse structures remained elusive.…”