UNSATURATED MACROCYCLIC COMPOUNDS. XII.1SYNTHESIS OF TWO COMPLETELY CONJUGATED THIRTY-MEMBERED RING CYCLIC SYSTEMS

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<i> </i>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<i> </i>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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Catalytic Synthesis of Cyclic Guanidines via Hydrogen Atom Transfer and Radical-Polar Crossover

10.26434/chemrxiv.13318421.v1 ◽

2020 ◽

Author(s):

Shunya Ohuchi ◽

Hiroki Koyama ◽

Hiroki Shigehisa

Keyword(s):

Hydrogen Atom ◽

Functional Group ◽

Hydrogen Atom Transfer ◽

Catalytic Synthesis ◽

Membered Ring ◽

Biologically Active ◽

Atom Transfer ◽

Powerful Method ◽

Protective Groups ◽

The Common

A catalytic synthesis of cyclic guanidines, which are found in many biologically active compounds and natu-ral products, was developed, wherein transition-metal hydrogen atom transfer and radical-polar crossover were employed. This mild and functional-group tolerant process enabled the cyclization of alkenyl guanidines bearing common protective groups, such as Cbz and Boc. This powerful method not only provided the common 5- and 6-membered rings but also an unusual 7-membered ring. The derivatization of the products afforded various heterocycles. We also investigated the se-lective cyclization of mono-protected or hetero-protected (TFA and Boc) alkenyl guanidines and their further derivatiza-tions.

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