Lecture 17 Friday February 20 2015 9 16 AM Synthesis of diols This is catalytic variant of the reaction shown above OsO4 is used in catalytic amounts Notice that the stereochemistry of the diol is cis The two OH s are delivered to the same face of the alkene Reactions of alcohols Ether formation Ester formation For export Page 1 Lecture 17 Friday February 20 2015 9 20 AM Ester formation ester Dean Stark Water is removed as an azeotrop with benzene using Dean Stark apparatus Esters can be formed from other derivatives of carboxylic acids under milder conditions For that are particularly useful acid chlorides and anhydrides which have good leaving groups attached to the carbonyl carbon Oxidations These two reagents allow us to stop the oxidation at the stage of the aldehyde and avoid the formation of the carboxylic acid For export Page 2 Lecture 17 Friday February 20 2015 9 25 AM Mechanism There are alternatives to using chromium next page For export Page 3 Lecture 17 Friday February 20 2015 9 27 AM Swern oxidation Overall reaction This reaction works for the oxidation of primary alcohols to aldehydes and secondary alcohols to ketones Mechanism Formation of the reactive regent Activation of the alcohol Oxidation For export Page 4 Lecture 17 Friday February 20 2015 9 33 AM Third way to oxidize alcohols to ketones or aldehydes Overall reaction This reaction can be used in synthesis of both aldehydes and ketones from primary and secondary alcohols Mechanism Activation of tempo Alcohol activation Oxidation Regeneration of the reagent For export Page 5 because this molecule is regenerated at the end of the reaction we can use TEMPO as a catalyst
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