Studies on vitamin D (calciferol) and its analogs. 29. Mechanistic studies by deuterium labeling and related kinetic investigations of the [1,5]-sigmatropic hydrogen shift of vitamin D type vinylallenes

Zirconium dialkyl complexes of the general formula fc(NPiPr2)2ZrR2 (where fc = 1,1′-ferrocenyl, R = CH3, CH2Ph, CH2tBu, tBu) have been synthesized and characterized via the addition of alkyl lithium or potassium benzyl derivatives to the dichloride complex fc(NPiPr2)2ZrCl2(THF). Addition of 2,6-dimethylphenylisocyanide to these alkyl derivatives generates the corresponding mono iminoacyl alkyl zirconium complexes. On thermolysis, the iminoacyl moiety containing a benzyl substituent undergoes rearrangement to yield a new complex that contains an alkene-amido fragment. Mechanistic studies point to a 1,2 hydrogen shift as the rate-determining step.

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A Simple Iron-Catalyst for Alkenylation of Ketones Using Primary Alcohols

Molecules ◽

10.3390/molecules25071590 ◽

2020 ◽

Vol 25 (7) ◽

pp. 1590

Author(s):

Motahar Sk ◽

Ashish Kumar ◽

Jagadish Das ◽

Debasis Banerjee

Keyword(s):

Quantitative Determination ◽

Iron Catalyst ◽

Mechanistic Studies ◽

Primary Alcohols ◽

Deuterium Labeling ◽

Produce Water ◽

Dehydrogenative Coupling

Herein, we developed a simple iron-catalyzed system for the α-alkenylation of ketones using primary alcohols. Such acceptor-less dehydrogenative coupling (ADC) of alcohols resulted in the synthesis of a series of important α,β-unsaturated functionalized ketones, having aryl, heteroaryl, alkyl, nitro, nitrile and trifluoro-methyl, as well as halogen moieties, with excellent yields and selectivity. Initial mechanistic studies, including deuterium labeling experiments, determination of rate and order of the reaction, and quantitative determination of H2 gas, were performed. The overall transformations produce water and dihydrogen as byproducts.

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Cobalt-catalyzed deoxygenative triborylation of allylic ethers to access 1,1,3-triborylalkanes

Nature Communications ◽

10.1038/s41467-020-19039-7 ◽

2020 ◽

Vol 11 (1) ◽

Cited By ~ 1

Author(s):

Wei Jie Teo ◽

Xiaoxu Yang ◽

Yeng Yeng Poon ◽

Shaozhong Ge

Keyword(s):

Building Blocks ◽

Mechanistic Studies ◽

Deuterium Labeling ◽

Bond Forming ◽

Carbon Carbon Bond ◽

Synthetic Utility ◽

Reaction Proceeds ◽

Site Selective ◽

And Control ◽

Allylic Ethers

Abstract Polyborylated organic compounds have been emerging as versatile building blocks in chemical synthesis. Here we report a selective cobalt-catalyzed deoxygenative 1,1,3-triborylation reaction of allylic ethers with pinacolborane to prepare 1,1,3-triborylalkane compounds. With naturally abundant and/or synthetic cinnamic methyl ethers as starting materials, we have achieved the synthesis of a variety of 1,1,3-triborylalkanes (25 examples). The synthetic utility of these 1,1,3-triborylalkanes is demonstrated through site-selective allylation, protodeborylation, and consecutive carbon-carbon bond-forming reactions. Mechanistic studies including deuterium-labeling and control experiments suggest that this 1,1,3-triborylation reaction proceeds through initial cobalt-catalyzed deoxygenative borylation of allylic ethers to form allylic boronates followed by cobalt-catalyzed 1,1-diborylation of the resulting allylic boronates.

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