Unsaturated Bond-Containing Heterochain Polymers for Biomedical Use

Recoverable Phospha-Michael Additions Catalyzed by a 4-N,N-Dimethylaminopyridinium Saccharinate Salt or a Fluorous Long-Chained Pyridine: Two Types of Reusable Base Catalysts

Molecules ◽

10.3390/molecules26041159 ◽

2021 ◽

Vol 26 (4) ◽

pp. 1159

Author(s):

Eskedar Tessema ◽

Vijayanath Elakkat ◽

Chiao-Fan Chiu ◽

Jing-Hung Zheng ◽

Ka Long Chan ◽

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Keyword(s):

Michael Addition ◽

Polar Solvent ◽

Addition Reaction ◽

High Yield ◽

Addition Reactions ◽

Polar Solvents ◽

Unsaturated Bond ◽

Base Catalysts ◽

Michael Additions

Phospha-Michael addition, which is the addition reaction of a phosphorus-based nucleophile to an acceptor-substituted unsaturated bond, certainly represents one of the most versatile and powerful tools for the formation of P-C bonds, since many different electrophiles and P nucleophiles can be combined with each other. This offers the possibility to access many diversely functionalized products. In this work, two kinds of basic pyridine-based organo-catalysts were used to efficiently catalyze phospha-Michael addition reactions, the 4-N,N-dimethylaminopyridinium saccharinate (DMAP·Hsac) salt and a fluorous long-chained pyridine (4-Rf-CH2OCH2-py, where Rf = C11F23). These catalysts have been synthesized and characterized by Lu’s group. The phospha-Michael addition of diisopropyl, dimethyl or triethyl phosphites to α, β-unsaturated malonates in the presence of those catalysts showed very good reactivity with high yield at 80–100 °C in 1–4.5 h with high catalytic recovery and reusability. With regard to significant catalytic recovery, sometimes more than eight cycles were observed for DMAP·Hsac adduct by using non-polar solvents (e.g., ether) to precipitate out the catalyst. In the case of the fluorous long-chained pyridine, the thermomorphic method was used to efficiently recover the catalyst for eight cycles in all the reactions. Thus, the easy separation of the catalysts from the products revealed the outstanding efficacy of our systems. To our knowledge, these are good examples of the application of recoverable organo-catalysts to the DMAP·Hsac adduct by using non-polar solvent and a fluorous long-chained pyridine under the thermomorphic mode in phospha-Michael addition reactions.

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Heterochain Polymers

Principles of Polymer Systems ◽

10.1201/b17873-20 ◽

2014 ◽

pp. 703-744

Keyword(s):

Heterochain Polymers

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Factors Promoting Alkene Migratory Insertion into Metal-Nitrogen Bond during Hydroamination in Recent Studies

Mini-Reviews in Organic Chemistry ◽

10.2174/1570193x18666210909110109 ◽

2021 ◽

Vol 18 ◽

Author(s):

Wenlai Han

Keyword(s):

Transition Metal ◽

Late Transition Metal ◽

Electronic Effects ◽

Metal Centers ◽

Unsaturated Bond ◽

Factors Influencing ◽

Migratory Insertion ◽

Late Transition ◽

Metal Catalyzed ◽

Nitrogen Bond

: Migratory insertion is a fundamental organometallic transformation that enables the functionalization of an unsaturated bond. Recent reports on catalytic hydroamination provide evidence that supports an intermolecular migratory insertion pathway featuring alkene insertion into metal-nitrogen (M-N) bonds. This article presents factors influencing the rate of migratory insertion in late-transition metal-catalyzed hydroamination, including steric and electronic effects from ligands, alkenes, and metal centers, along with stabilization from coordinated amine intermediates and ordered transition states.

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