Bis(amino)cyclopropenylidene-Catalyzed 1,6-Conjugate Addition of Aromatic Aldehydes to <i>para</i>-Quinone Methides: Expedient Access to α,α′-Diarylated Ketones

Ramanjaneyulu, Bandaru T.; Mahesh, Sriram; Anand, Ramasamy Vijaya

doi:10.1021/acs.orglett.5b01724

Cited by 116 publications

(35 citation statements)

References 80 publications

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“…Efforts to develop non five-membered nitrogen-containing heterocyclic carbenes have been rather limited as a consequence of the success of NHCs. However, bis(amino)-cyclopropenylidenes (BACs), the smallest aromatic rings containing a carbene center, have recently been employed in some intriguing applications [33,34]. Easily prepared in a one-pot reaction, BACs, likewise NHCs, catalytically induce acyl anion reactivity in aldehydes.…”

Section: Use Of Bis(amino)-cyclopropenylidenes (Bacs)mentioning

confidence: 99%

An Overview on the N-Heterocyclic Carbene-Catalyzed Aza-Benzoin Condensation Reaction

Albanese

Gaggero

2018

Catalysts

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Abstract:The N-heterocyclic carbene(NHCs)-catalyzed aza-benzoin condensation reaction is an efficient, single step strategy which employs easily available substrates, such as aldehydes and imines, to provide α-amino ketones. The multifunctionality and high reactivity of α-amino ketones makes these structures attractive for medicinal chemistry and as precursors of a variety of amine derivatives. The different electrophilic characteristics of aldehydes and imines ensure a high regioselective reaction. Enantiomerically-enriched α-amino ketones have been synthesized through stereoselective couplings promoted by chiral N-heterocyclic carbenes. One-pot domino procedures, including an aza-benzoin step, allow valuable complex molecules to be accessed.

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Section: Use Of Bis(amino)-cyclopropenylidenes (Bacs)mentioning

confidence: 99%

An Overview on the N-Heterocyclic Carbene-Catalyzed Aza-Benzoin Condensation Reaction

Albanese

Gaggero

2018

Catalysts

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“…受到这些报道的启发, 我们设想将可见光氧化还原自催化体系应用到 α-酮酸与对位亚甲基醌 (p-QMs) [14] 发生脱羧、1,6-共轭加成反应, 从而实现 α-芳基-α,α′-二芳基酮的合成(图 1b). 这个合成策略不同于已知文献报道的使用氮杂卡宾小分子催化下得到芳基甲酰基负离子的途径 [4] , 该反应所需要的催化剂当量相对较低, 反应通过芳基甲酰基自由基活性中间体, 反应普适性也有较大不同. 本文报道了我们实验探究所获得的一些结果.…”

Section: Equiv的 Nhc 催化剂参与反应(图 1a)unclassified

Decarboxylative 1,6-Conjugate Addition of α-Keto Acids with para-Quinone Methides Enabled by Photoredox Catalysis

吴自俊¹,

汪舰²

2017

Acta Chim. Sinica

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Arylated and α,α'-diarylated carbonyls are an important class of building blocks and widely found in biologically active natural and unnatural molecules. The most popular approach to access α-arylated and α,α′-diarylated carbonyls involves transition-metal-catalyzed cross-coupling reactions and metal-free coupling reactions, which always request harsh conditions or high catalytic loading. Visible-light photoredox catalysis, a novel and green catalytic strategy, has recently received increasing attention from chemists and been widely applied to organic synthesis in the past years. Inspired by the recent process of the visible light photocatalytic generation and exploration of α-keto acids as the precursor for acyl radical in decarboxylative coupling reactions and 1,4-Michael addition reactions, we found that, however, expand their utilization in more complex systems, such as 1,6-conjugate addition with electron deficient olefins, remains underdeveloped, particularly due to the difficult to design the appropriate substrate, and the harsh conditions often required for metal-catalyzed redox neutral decarboxylation. Here, we report a photoredox catalytic CC bond formation reaction that enabled by visible-light. The versatility of this protocol has been portrayed by using a wide range of stable and easily accessible aromatic α-keto acids as well as p-QMs. This synthetic strategy also offers access to 24 kinds of different α-keto-α,α'-diarylated ketones in moderate to excellent yields under mild conditions. A representative procedure for the reaction is as follows: 2-oxo-2-phenylacetic acid 1a (0.10 mmol), the p-QM (2,6-di-tert-butyl-4-(4-methoxybenzylidene)cyclohexa-2,5-dien-1-one) 2a (0.12 mmol), photocatalyst Ir[dF(CF 3)PPy] 2 (dtbbpy)PF 6 (0.001 mmol) and K 2 HPO 4 (0.12 mmol) were dissolved in DCM (1 mL). Then, the resulting mixture was degassed and refilled with N 2 via 'freeze-pump-thaw' procedure (3 times). After that, the solution was stirred at a distance of ca. 5 cm from a 36 W blue LEDs at room temperature for about 12 h with TLC monitoring. Upon completion of the reaction, the crude product was purified by flash chromatography on silica gel (hexane/ethyl acetate) to give the desired product 3.

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“…[69] The authors were able to exploit the susceptibility of p-QMs to undergo aromatization, whilst utilizing BAC 233 for the umpolung activation of aromatic and heteroaromatic aldehydes.D iarylated ketone products 249 were synthesized in good to excellent yields (Scheme 34). [69] The authors were able to exploit the susceptibility of p-QMs to undergo aromatization, whilst utilizing BAC 233 for the umpolung activation of aromatic and heteroaromatic aldehydes.D iarylated ketone products 249 were synthesized in good to excellent yields (Scheme 34).…”

Section: Catalysis With Bis(amino)cyclopropenylidenesmentioning

confidence: 99%

“…In 2015, Anand and co-workers reported that BACs were useful as promotors for the 1,6-conjugate addition of aldehydes 247 to para-quinone methides (p-QM) 248. [69] The authors were able to exploit the susceptibility of p-QMs to undergo aromatization, whilst utilizing BAC 233 for the umpolung activation of aromatic and heteroaromatic aldehydes.D iarylated ketone products 249 were synthesized in good to excellent yields (Scheme 34). Anand and co-workers, in as imilar manner to the previous studies of Wilde and Gravel, [67,68] compared the effectiveness of the BACc atalyst to commonly employed NHCs for similar reactions,and were able to show that the performance of 233 was superior to that of the NHCs.A lthough the essence of the chemical transformation is conceptually analogous to that of Wilde and Gravel, Anand and co-workers cleverly designed the reaction substrates such that they ended up with atotally different set of products.H owever,t hey did not report any attempt at asymmetric synthesis.…”

Section: Angewandte Chemiementioning

confidence: 99%

Promotion of Organic Reactions by Non‐Benzenoid Carbocyclic Aromatic Ions

et al. 2016

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The first three primary members of the non-benzenoid carbocyclic aromatic ion family, namely cyclopropenium, cyclopentadienide, and cycloheptatrienium (tropylium) ions, have planar cyclic structures with (4n+2)π electrons in fully conjugated systems. They fulfill Hückel's rule for aromaticity and hence possess extraordinary stability. Since the historic discovery of tropylium bromide in the late 19th Century, these non-benzenoid aromatic ions have attracted a lot of attention because of their unique combination of stability and reactivity. The charge on the aromatic ions makes them more prone to nucleophilic/electrophilic reactions than the neutral benzenoid counterparts. Within the last seven years, there has been a large number of investigations in utilizing aromatic ions to mediate organic reactions. This Review highlights these recent developments and discusses the potential of aromatic ions in promoting synthetically useful organic transformations.

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Bis(amino)cyclopropenylidene-Catalyzed 1,6-Conjugate Addition of Aromatic Aldehydes to para-Quinone Methides: Expedient Access to α,α′-Diarylated Ketones

Cited by 116 publications

References 80 publications

An Overview on the N-Heterocyclic Carbene-Catalyzed Aza-Benzoin Condensation Reaction

An Overview on the N-Heterocyclic Carbene-Catalyzed Aza-Benzoin Condensation Reaction

Decarboxylative 1,6-Conjugate Addition of α-Keto Acids with para-Quinone Methides Enabled by Photoredox Catalysis

Promotion of Organic Reactions by Non‐Benzenoid Carbocyclic Aromatic Ions

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