Abstract:A domino synthesis of benzofurans with the modification of side chains from α-alkoxyalkyl o-alkynylaryl ethers (n = 0) and electron-rich arenes has been developed. In the present domino reaction, which would proceed via the α-alkoxyalkylation of arenes with an intermediate in the migratory cycloisomerization of o-alkynylaryl ethers followed by the nucleophilic addition of benzofurans to benzyl ethers, a cationic Au(III) catalyst activates the C-C π bond and the C-O σ bond. The present method could be extended … Show more
“…Later, Saito et al . disclosed a domino synthesis of tetracyclic isochroman derivatives from α‐alkoxyalkyl ( o ‐alkynylaryl)methyl ethers and arenes using Gagosz gold catalyst (Ph 3 PAuNTf 2 ), in which the entire reaction is spurred by an initial Au(I)‐mediated 6‐ endo ‐ dig selective cyclization [163] . Quite similar to this report, the combined asymmetric organo/Au(I)‐catalysis in a relay process affords epimeric bicyclic O , O ‐acetals through 6‐ endo ‐ dig selective cyclization [164] .…”
Section: Cyclization Of Oxygen Tethered C−c Multiple Bondsmentioning
Since the dawn of millennium, catalytic gold chemistry is at the forefront to set off diverse organic reactions via unique activation of π‐bonded molecules. Within this purview, cycloisomerization of heteroatom nucleophiles linked to a π‐system is one of the well recognized chemistry for the construction of numerous heterocyclic cores. Though the rudimentary aspects of this transformation are reviewed by several groups in different timeline, a holistic view on regiochemistry of such reactions went largely overlooked. Hence, this account emphasizes the gold catalyzed regioselective cycloisomerization of structurally distinctive π‐connected hetero‐nucleophiles leading to different heterocycles documented in the last two decades. From an application perspective, this account also highlights those methodologies which find a role in the total synthesis of natural products. Wherever appropriate, mechanistic details and contributing factors for selectivity are also discussed.
“…Later, Saito et al . disclosed a domino synthesis of tetracyclic isochroman derivatives from α‐alkoxyalkyl ( o ‐alkynylaryl)methyl ethers and arenes using Gagosz gold catalyst (Ph 3 PAuNTf 2 ), in which the entire reaction is spurred by an initial Au(I)‐mediated 6‐ endo ‐ dig selective cyclization [163] . Quite similar to this report, the combined asymmetric organo/Au(I)‐catalysis in a relay process affords epimeric bicyclic O , O ‐acetals through 6‐ endo ‐ dig selective cyclization [164] .…”
Section: Cyclization Of Oxygen Tethered C−c Multiple Bondsmentioning
Since the dawn of millennium, catalytic gold chemistry is at the forefront to set off diverse organic reactions via unique activation of π‐bonded molecules. Within this purview, cycloisomerization of heteroatom nucleophiles linked to a π‐system is one of the well recognized chemistry for the construction of numerous heterocyclic cores. Though the rudimentary aspects of this transformation are reviewed by several groups in different timeline, a holistic view on regiochemistry of such reactions went largely overlooked. Hence, this account emphasizes the gold catalyzed regioselective cycloisomerization of structurally distinctive π‐connected hetero‐nucleophiles leading to different heterocycles documented in the last two decades. From an application perspective, this account also highlights those methodologies which find a role in the total synthesis of natural products. Wherever appropriate, mechanistic details and contributing factors for selectivity are also discussed.
“…[9] To improve synthetic efficiency and allow functionalization at less-reactive positions, domino reactions constitutea na ttractive strategy. [10] For example, the formation of the heterocycle and another CÀCb ond at the C3 position was employed to synthesize alkenyl-, aryl-or alkyl-C3-substituted benzofurans using Pd [11] or Rh [12] catalysis, and C3 alkyl or aryl benzothiophenes and benzofurans through Au/Pt [13] or Pd [14] catalysis. To our surprise, ac yclization-alkynylation domino process was unprecedented.…”
Thienoacenes and furoacenes are among the most frequent molecular units found in organic materials. The efficient synthesis of morphologically different heteroacenes and the rapid determination of their solid-statea nd electronic properties are still challenging tasks, which slow down progress in the development of new materials. Here, we report af lexible and efficient synthesis of unprecedented heterotetracenes based on ap latinum-and gold-catalyzed cyclization-alkynylation domino process using EthynylBenziodoXole (EBX) hypervalent iodine reagents in the key step. The proof-of-principlei ns ilico estimation of the synthesized tetracenes'c harget ransport properties reveals their strong dependence on both the positionand nature of the heteroatoms in the ring system.Abroad range of mobility is predicted, with some compounds displaying performance potentiallyc omparable to that of state-of-the-art electronic organic materials.
“…Thus, the development of a general and stereoselective method towards a rapid construction is highly desirable. However, to our knowledge, such an effient methodology has not yet been established so far 6 , probably due to the inherent instability of tetracyclic isochroman polyketide and the difficulties in controlling the complex stereochemistry. Fig.…”
Polyketide oligomers containing the structure of tetracyclic isochroman comprise a large class of natural products with diverse activity. However, a general and stereoselective method towards the rapid construction of this structure remains challenging due to the inherent instability and complex stereochemistry of polyketide. By mimicking the biosynthetic pathway of this structurally diverse set of natural products, we herein develop an asymmetric hetero-Diels–Alder reaction of in-situ generated isochromene and ortho-quinonemethide. A broad range of tetracyclic isochroman frameworks are prepared in good yields and excellent stereoinduction (up to 95% ee) from readily available α-propargyl benzyl alcohols and 2-(hydroxylmethyl) phenols under mild conditions. This direct enantioselective cascade reaction is achieved by a Au(I)/chiral Sc(III) bimetallic catalytic system. Experimental studies indicate that the key hetero-Diels-Alder reaction involves a stepwise pathway, and the steric hindrance between in-situ generated isochromene and t-Bu group of Sc(III)/N,N’-dioxide complex is responsible for the enantioselectivity in the hetero-Diels–Alder reaction step.
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