Mukaiyama Aldol Reaction Catalyzed by (Benz)imidazolium-Based Halogen Bond Donors

10.26434/chemrxiv.12820652 ◽

2020 ◽

Author(s):

Revannath L. Sutar ◽

Nikita Erochok ◽

Stefan Huber

Keyword(s):

Halogen Bond ◽

Aldol Reaction ◽

Mukaiyama Aldol Reaction ◽

Mukaiyama Aldol ◽

Background Reaction ◽

Strong Performance ◽

The Stability ◽

Elemental Iodine

A series of cationic monodentate and bidentate iodo(benz)imidazolium-based halogen bond (XB) donors were employed as catalysts in a Mukaiyama aldol reaction. While 5 mol% of a monodentate variant showed noticeable activity, a syn-preorganized bidentate XB donor provided a strong performance even with 0.5 mol% loading. In contrast to the very active BArF4 salts, PF6 or OTf salts were either inactive or showed background reaction. Repetition experiments clearly ruled out a potential hidden catalysis by elemental iodine and demonstrated the stability of our catalyst over three consecutive cycles.

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Mukaiyama aldol reaction catalyzed by (benz)imidazolium-based halogen bond donors

Organic & Biomolecular Chemistry ◽

10.1039/d0ob02503h ◽

2021 ◽

Vol 19 (4) ◽

pp. 770-774

Author(s):

Revannath L. Sutar ◽

Nikita Erochok ◽

Stefan M. Huber

Keyword(s):

High Efficiency ◽

Halogen Bond ◽

Aldol Reaction ◽

Mukaiyama Aldol Reaction ◽

Mukaiyama Aldol ◽

Very High

A Mukaiyama aldol reaction can be catalyzed by bidentate halogen bond donors with very high efficiency. The halogenated catalysts were stable over multiple consecutive runs, which supports the halogen-bond-based mode of catalysis.

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Modern Synthesis and Chemistry of Stabilized, Ketene N,O-Acetals

Synthesis ◽

10.1055/a-1713-8481 ◽

2021 ◽

Author(s):

Timothy J. Paris ◽

Rachel Willand-Charnley

Keyword(s):

Aldol Reaction ◽

Diels Alder ◽

First Century ◽

Mukaiyama Aldol Reaction ◽

Ability To Act ◽

Mukaiyama Aldol ◽

Recent Developments ◽

Electron Withdrawing Group ◽

The Stability

Ketene N,O-acetals are robust and versatile synthons. Herein, we outline the synthesis of stable ketene N,O-acetals in the twenty-first century. In addition, we review recent developments in the chemistry of ketene N,O-acetals, as it applies to the vinylogous Mukaiyama aldol reaction, electrolysis, and pericyclic transformations. While dated reports rely on in situ use, modern methods of ketene N,O-acetal synthesis are heavily oriented towards producing products with high “bench” stability; moreover, in the present century, chemists typically enhance the stability of ketene N,O-acetals by positioning an electron-withdrawing group at the β-terminus or at the N-position. As propitious substrates in the vinylogous Mukaiyama aldol reaction, ketene N,O-acetals readily provide polyketide adducts with high regioselectivity. When exposed to electrolysis conditions, the title functional group forms a reactive radical cation and cleanly couples with a variety of activated olefins. Given their electron-rich nature, ketene N,O-acetals act as facile substrates in several rearrangement reactions; further, ketene N,O-acetals reserve the ability to act as either dienophiles or dienes in Diels-Alder reactions. Lastly, ketene N,O-acetals are seemingly more stable than their O,O- counterparts and more reactive than analogous N,N- or S,S-acetals; these factors, in combination, make ketene N,O-acetals advantageous substitutes for other ketene acetal homologs.

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Design and Synthesis of a Chiral Halogen-Bond Donor with a Sp3-Hybridized Carbon–Iodine Moiety in a Chiral Fluorobissulfonyl Scaffold

Molecules ◽

10.3390/molecules25194539 ◽

2020 ◽

Vol 25 (19) ◽

pp. 4539

Author(s):

Hiroto Uno ◽

Kohei Matsuzaki ◽

Motoo Shiro ◽

Norio Shibata

Keyword(s):

Halogen Bond ◽

Aldol Reaction ◽

Asymmetric Induction ◽

Nmr Titration ◽

Titration Experiment ◽

Mukaiyama Aldol Reaction ◽

Design And Synthesis ◽

Mukaiyama Aldol

The first example of a chiral halogen-bond donor with a sp3-hybridized carbon–iodine moiety in a fluorobissulfonyl scaffold is described. The binaphthyl backbone was designed as a chiral source and the chiral halogen-bond donor (R)-1 was synthesized from (R)-1,1′-binaphthol in 11 steps. An NMR titration experiment demonstrated that (R)-1 worked as a halogen-bond donor. The Mukaiyama aldol reaction and quinoline reduction were examined using (R)-1 as a catalyst to evaluate the asymmetric induction.

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