New inexpensive polymer supported reagents based on polysiloxanes
Using polymethylhydrosiloxane (PMHS) 1, a commercially available free flowing liquid, the formation of crosslinked polymers 3 using a crosslinker 2 and a variety of catalysts such as Wilkinson's, TBAF and diethylhydroxylamine to aid this process are reported. The application of these polymers to the reduction of acetophenone is also discussed. Secondly, crosslinked PMHS resins incorporating DMAP 4 and pyridine derivatives 5 were developed as scavengers. Both resins were found to successfully scavenge benzyl bromide. Studies using various substrates are discussed along with resin compositions giving indications of loading. The resins were found to be active towards benzyl halides and cinnamyl halides. A comparison is also made between the resins made in house and those available commercially. Aldehyde resins 6 were also developed to scavenge amines. This was found to be successful in scavenging benzylamine and other amine derivatives. An in situ method to scavenge aldehydes is also described. Using the substrate and the scavenging hydrazine 7 in solution, crosslinked PMHS was then used to remove the imine intermediate 8 successfully from solution. Finally, studies were performed using an in situ polymerisation method to scavenge for alcohols 9 and other substrates from solution along with a 3 component scavenging study. PMHS was used to successfully scavenge various alcohols from 1:1 standard solutions in the presence of 1,4-benzenedimethanol 2 and diethylhydroxylamine catalyst giving species such as 11. Tzu-hsia said, A man who Treats his betters as betters Wears an air of respect, Who into serving father and mother Knows how to put his whole strength, Who in the service of the prince will lay down his life, Who in interaction with friends is true to his word - others may say of him that he still lacks education, but I for my part should certainly call him an educated man. Confucius.
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