1‐Methylimidazole 3‐N‐Oxide as a New Promoter for the Morita—Baylis—Hillman Reaction.

Lin, Yu‐Sheng; Liu, Chih‐Wei; Tsai, T. Y. R.

doi:10.1002/chin.200527089

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“…Based on the proposed type IV mechanism in Scheme 2, catalytic activity of BD is expected. Although BNO [18,19] can't function asymmetrically alone, aliphatic N-oxides [11,36] have been known as a good nucleophile. N-oxides are easy to synthesize and preserve.…”

Section: Resultsmentioning

confidence: 99%

“…Base the proposed type IV mechanism in Scheme 2, catalytic activity of BD is expected. hough BNO [18,19] can't function asymmetrically alone, aliphatic N-oxides [11,36] h been known as a good nucleophile. N-oxides are easy to synthesize and prese Therefore, BNO was also considered as a co-catalyst with BD for asymmetric reac Herein, we report the investigation of catalytic ability of BD alone and BD with BNO co-catalyst in asymmetric MBH reaction.…”

Section: Scheme 1 Brucine Derivatives In Asymmetric Synthesismentioning

confidence: 99%

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Brucine Diol-Catalyzed Enantioselective Morita-Baylis-Hillman Reaction in the Presence of Brucine N-Oxide

2021

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Brucine diol (BD) catalyzed asymmetric Morita–Baylis–Hillman (MBH) reaction is observed for the first time. Brucine N-oxide (BNO) was found to not have an effective chiral catalyst. Faster reaction rate was obtained using unsaturated ester or aromatic aldehydes in the presence of BNO. 4-Nitrobenzaldehyde and α,β-unsaturated ketone/ester were converted to the MBH adduct in moderate yields (up to 74%) with 70% ee value by this catalytic system. The mechanism of BD catalysis is probably initiated by conjugating the vicinal diol of BD to the carbonyl group of the aromatic aldehyde through hydrogen bonding. The tertiary amine of BD acts as a nucleophile to activate vinyl ketone for coupling with the carbonyl of aldehyde through an intramolecular carbonylated reaction. Finally, the breakdown of the complex caused the formation of the MBH adduct (a benzyl-allyl alcohol). The chirality of the benzyl-allyl alcohol is likely affected by the interaction of the bulky asymmetric plane of BD.

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