scholarly journals Kinetic and mechanistic studies of reactive intermediates in photochemical and transition metal-assisted oxidation, decarboxylation and alkyl transfer reactions

2014 ◽  
Author(s):  
Jack McCaslin Carraher
Keyword(s):  
Transition Metal ◽  
Reactive Intermediates ◽  
Transfer Reactions ◽  
Mechanistic Studies ◽  
Alkyl Transfer

scholarly journals Chain Transfer to Solvent and Monomer in Early Transition Metal Catalyzed Olefin Polymerization: Mechanisms and Implications for Catalysis

Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 215
Author(s):  
Francesco Zaccaria ◽  
Peter H. M. Budzelaar ◽  
Cristiano Zuccaccia ◽  
Roberta Cipullo ◽  
Alceo Macchioni ◽  
...  
Keyword(s):  
Transition Metal ◽  
Chain Transfer ◽  
Olefin Polymerization ◽  
Transfer Reactions ◽  
Organic Radical ◽  
Mechanistic Studies ◽  
Early Transition Metal ◽  
Polymerization Catalysis ◽  
Insertion Polymerization ◽  
Early Transition

Even after several decades of intense research, mechanistic studies of olefin polymerization by early transition metal catalysts continue to reveal unexpected elementary reaction steps. In this mini-review, the recent discovery of two unprecedented chain termination processes is summarized: chain transfer to solvent (CTS) and chain transfer to monomer (CTM), leading to benzyl/tolyl and allyl type chain ends, respectively. Although similar transfer reactions are well-known in radical polymerization, only very recently they have been observed also in olefin insertion polymerization catalysis. In the latter context, these processes were first identified in Ti-catalyzed propene and ethene polymerization; more recently, CTS was also reported in Sc-catalyzed styrene polymerization. In the Ti case, these processes represent a unique combination of insertion polymerization, organic radical chemistry and reactivity of a M(IV)/M(III) redox couple. In the Sc case, CTS occurs via a σ-bond metathesis reactivity, and it is associated with a significant boost of catalytic activity and/or with tuning of polystyrene molecular weight and tacticity. The mechanistic studies that led to the understanding of these chain transfer reactions are summarized, highlighting their relevance in olefin polymerization catalysis and beyond.

scholarly journals Transition-Metal-Free Boryl Substitution Using Silylboranes and Alkoxy Bases

Synlett ◽  
2017 ◽  
Vol 28 (11) ◽  
pp. 1258-1267 ◽  
Author(s):  
Hajime Ito ◽  
Eiji Yamamoto ◽  
Satoshi Maeda ◽  
Tetsuya Taketsugu
Keyword(s):  
Transition Metal ◽  
Functional Group ◽  
Experimental Studies ◽  
Transition Metal Catalysts ◽  
Alkyl Halides ◽  
Aryl Halides ◽  
Nucleophilic Attack ◽  
Important Class ◽  
Mechanistic Studies ◽  
Induced Reaction

Silylboranes are used as borylation reagents for organohalides in the presence of alkoxy bases without transition-metal catalysts. PhMe2Si–B(pin) reacts with a variety of aryl, alkenyl, and alkyl halides, including sterically hindered examples, to provide the corresponding organoboronates in good yields with high borylation/silylation ratios, showing good functional group compatibility. Halogenophilic attack of a silyl nucleophile on organohalides, and subsequent nucleophilic attack on the boron electrophile are identified to be crucial, based on the results of extensive theoretical and experimental studies. This boryl­ation reaction is further applied to the first direct dimesitylboryl (BMes2) substitution of aryl halides using Ph2MeSi–BMes2 and Na(O-t-Bu), affording aryldimesitylboranes, which are regarded as an important class of compounds for organic materials.1 Introduction2 Boryl Substitution of Organohalides with PhMe2Si–B(pin)/Alkoxy Bases3 Mechanistic Investigations4 DFT Mechanistic Studies Using an Artificial Force Induced Reaction (AFIR) Method5 Dimesitylboryl Substitution of Aryl Halides with Ph2MeSi–BMes2/Na(O-t-Bu)6 Conclusion

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