- One pot tandem dual CC and CO bond reductions in the β-alkylation of secondary alcohols with primary alcohols by ruthenium complexes of amido and picolyl functionalized N-heterocyclic carbenes
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Two different classes of ruthenium complexes, namely, [1-mesityl-3-(2,6-Me2-phenylacetamido)-imidazol-2-ylidene]Ru(p-cymene)Cl (1c) and {[1-(pyridin-2-ylmethyl)-3-(2,6-Me2-phenyl)-imidazol-2-ylidene]Ru(p-cymene)Cl}Cl (2c), successfully catalyzed the one-pot tandem alcohol-alcohol coupling reactions of a variety of secondary and primary alcohols, in moderate to good yields of ca. 63-89%. The mechanistic investigation performed on two representative catalytic substrates, 1-phenylethanol and benzyl alcohol using the neutral ruthenium (1c) complex showed that the catalysis proceeded via a partially reduced CC hydrogenated carbonyl species, [PhCOCH2CH2Ph] (3′), to the fully reduced CO and CC hydrogenated secondary alcohol, [PhCH(OH)CH2CH2Ph] (3). Furthermore, the time dependent study showed that the major product of the catalysis modulated between (3′) and (3) during the catalysis run performed over an extended period of 120 hours. Finally, the practical utility of the alcohol-alcohol coupling reaction was demonstrated by preparing five different flavan derivatives (13-17) related to various bioactive flavonoid natural products, in a one-pot tandem fashion.
- Dey, Shreyata,Ghosh, Prasenjit,Prakasham, A. P.,Ta, Sabyasachi
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p. 15640 - 15654
(2021/11/30)
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- Tandem Cross Coupling Reaction of Alcohols for Sustainable Synthesis of β-Alkylated Secondary Alcohols and Flavan Derivatives
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A Ru(II) NHC complex (loading down to 0.001 mol%) catalyzed cross coupling of a broad range of aromatic, aliphatic and heterocyclic alcohols is reported. This protocol also functioned efficiently under solvent-free conditions. Remarkably, this catalytic system disclosed so far the highest TON of 288000 for the cross coupling of alcohols. Notably, this methodology was successfully applied for the one-pot synthesis of a range of flavan derivatives. A detailed DFT studies and kinetic experiments were performed to understand the reaction mechanism as well as the high reactivity of this catalytic system. (Figure presented.).
- Shee, Sujan,Paul, Bhaskar,Panja, Dibyajyoti,Roy, Bivas Chandra,Chakrabarti, Kaushik,Ganguli, Kasturi,Das, Ayan,Das, Gourab Kanti,Kundu, Sabuj
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supporting information
p. 3888 - 3893
(2017/10/07)
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- A Modular Synthesis of 2-Alkyl- and 2-Arylchromans via a Three-Step Sequence
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A convergent three-step method for the synthesis of 2-substituted chromans is described. These results have been accomplished via the Heck coupling of readily accessible allylic alcohols and 2-iodophenols, followed by reduction and Mitsunobu cyclization. The utility and generality of this method is demonstrated through the synthesis of a series of 2-aryl-, 2-heteroaryl- and 2-alkylchromans, as well as an azachroman derivative. The asymmetric version of this approach via a Noyori-catalyzed ketone reduction and subsequent cyclization is likewise highlighted.
- Orr, Robert K.,Campeau, Louis-Charles,Chobanian, Harry R.,McCabe Dunn, Jamie M.,Pio, Barbara,Plummer, Christopher W.,Nolting, Andrew,Ruck, Rebecca T.
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p. 657 - 666
(2017/01/28)
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- Tosylhydrazine mediated conjugate reduction and sequential reductive coupling cyclization: Synthesis of 2-arylchromans
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Tosylhydrazine mediated conjugate reduction of 2-hydroxyl chalcones and sequential reductive coupling cyclization is described. This is an unprecedented protocol and an extremely efficient method for a one-pot domino synthesis of 2-arylchromans in good to excellent yields from commercially available, cheap starting materials. More importantly, the two-step reactions can be easily controlled to afford dihydrochalcones or 2-arylchromans by the mole amounts of tosylhydrazine. Furthermore, the operational simplicity of the process and the high functional group tolerance are remarkable.
- Shang, Xuyang,Zhou, Xiaomeng,Zhang, Wei,Wan, Changfeng,Chen, Junmin
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p. 8187 - 8193
(2015/12/30)
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- Transition metals catalyzed C-C and C-O bonds formation: Facile synthesis of flavans and benzoxepines
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A simple and practical method has been developed based on intermolecular [Pd]-catalyzed C-C and an intramolecular [Cu]-catalyzed C-O bond formations for the synthesis of flavans and benzoxepines. Interestingly, the method is amenable for the synthesis of
- Ramulu, B. Venkat,Mahendar,Krishna,Reddy, A. Gopi Krishna,Suchand,Satyanarayana
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p. 8305 - 8315
(2013/09/02)
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- An efficient intermolecular [Pd]-catalyzed C-C and intramolecular [Cu]-catalyzed C-O bonds formation: Synthesis of functionalized flavans and benzoxepine
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An efficient three-step strategy for the synthesis of functionalized flavans, starting from readily available 2-bromoiodobenzenes and aryl vinyl alcohols, is presented and successfully extended to benzoxepine. An intermolecular [Pd]-catalyzed C-C and an i
- Suchand,Krishna,Venkat Ramulu,Dibyendu,Gopi Krishna Reddy,Mahendar,Satyanarayana
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supporting information; experimental part
p. 3861 - 3864
(2012/08/14)
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