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 … Show more
“…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.…”
Photo-promoted mild tandem 6-exo-trig spirocyclization of biaryl ynones with ammonium thiocyanate has been developed to access thiocyanate-containing spiro[5,5]trienones with good yields and regioselectivity. Meanwhile, other thiocyanate-substituted cycles also could be...
“…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.…”
Photo-promoted mild tandem 6-exo-trig spirocyclization of biaryl ynones with ammonium thiocyanate has been developed to access thiocyanate-containing spiro[5,5]trienones with good yields and regioselectivity. Meanwhile, other thiocyanate-substituted cycles also could be...
“…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.…”
A copper-iron-based catalyst has been prepared by a low-temperature co-precipitation and sonication method. The use of high-energy ultrasound reduces the time required for the preparation process from one workweek to...
“…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 .…”
mentioning
confidence: 99%
“…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) .…”
mentioning
confidence: 99%
“…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.…”
A Rh(II)-catalyzed oxy-alkynylation of acceptor–acceptor
carbenes using EBX reagents was successfully developed. The key alkyne-transfer
step is likely to occur through a tandem process involving a β-addition,
an α-elimination, and a 1,2-shift, which was supported by the
formation of alkylidene carbene. Various diverse C2-quaternary alkyne-substituted
benzofuran-3-ones and 2,2,4,5-tetrasubstituted 3(2H)-furanones can be synthesized smoothly, depending on the choice
of diazo compounds and the base additives. Furthermore, this reaction
is characterized by mild conditions, high functional group compatibility,
and a broad substrate scope.
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