ENANTIOSELECTIVE CROSS ALDOL REACTION VIA DIVALENT TIN ENOLATE

An new overall lower energy pathway for the amine-catalysed Morita-Baylis-Hillman reaction is proposed from computations at the M06-2X/6-311++G(d,p) level. The pathway involves proton-transfer from the ammonium ion to the alkoxide formed from the aldol reaction through a seven-membered ring transition state (TS) structure followed by highly exothermic Hofmann elimination through a five-membered ring TS structure to form the product and also release the catalyst to carry on with the process all over again.

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An Alternate Energy-Conserved Pathway for the Morita-Baylis-Hillman (MBH) Reaction

10.26434/chemrxiv.12011673 ◽

2020 ◽

Author(s):

Veejendra Yadav

Keyword(s):

Proton Transfer ◽

Transition State ◽

Lower Energy ◽

Aldol Reaction ◽

Membered Ring ◽

Ammonium Ion ◽

Alternate Energy ◽

Ring Transition State ◽

Mbh Reaction

An new overall lower energy pathway for the amine-catalysed Morita-Baylis-Hillman reaction is proposed from computations at the M06-2X/6-311++G(d,p) level. The pathway involves proton-transfer from the ammonium ion to the alkoxide formed from the aldol reaction through a seven-membered ring transition state (TS) structure followed by highly exothermic Hofmann elimination through a five-membered ring TS structure to form the product and also release the catalyst to carry on with the process all over again.

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

10.26434/chemrxiv.12820652.v1 ◽

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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Synthesis of the C19–C30 Bis-THF Fragment of Iriomoteolide-13a via Stepwise SN2 Cyclization and Intramolecular syn-Oxypalladation

10.26434/chemrxiv.13506678.v1 ◽

2020 ◽

Author(s):

Hui Zhao ◽

Kai Gao ◽

Haichen Ma ◽

Tsz Chun Yip ◽

Wei-Min Dai

Keyword(s):

Aldol Reaction ◽

Allylic Alcohol ◽

Asymmetric Dihydroxylation ◽

Hydroxy Groups

The C19–C30 bis-THF fragment of the proposed structure of iriomoteolide-13a has been synthesized. The w-mesyloxy-substituted stereotetrad possessing three continuous hydroxy groups was generated by anti-aldol reaction and asymmetric dihydroxylation (AD). Upon heating in pyridine the stereotetrad underwent an SN2 cyclization to form the C19–C22 THF ring. It was followed by an intramolecular syn-oxypalladation of the C28 chiral allylic alcohol to give the C23–C26 THF ring.

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