Iodine-water-mediated Deprotective Oxidation Of Allylic Ethers

The reaction process of deprotection oxidation of allyl ether toa,b-unsaturated ketone and aldehyde has a wide range of practical applications in organic synthesis.The two-step method is mostly used of the methods of deprotection and oxidation currently.However,two-step method means that the ether protecting group is removed to be alcohol,and then the alcohol is oxidized to generate?,?-unsaturated aldehyde/ketone.The two-step method divides one step into two steps,which is not in line with the economics.The other method is one-pot method,?,?-unsaturated aldehydes and ketones can be obtained directly from allyl ethers which we call�one-step method'.But most of the reagents with one-step method used currently are highly toxic and difficult to handle.It's not only harmful to the human body but also harmful to the environment.In this study,we proposed for the first time that iodine as a deprotecting oxidation reagent and reacted in the presence of water.We developed a novel method that can directly convert allyl benzyl ether to?,?-unsaturated ketone.An aldehyde deprotection oxidation reaction system was applied to the deprotection oxidation reaction of allyl silyl ether,methyl ether,allyl ether and allyl ester.Two parts are showed:1. The conversion of allyl ether to allyl ketone/aldehyde is introduced in detail,and a large number of applications in the synthesis are exemplified.What's more,the limitation of the reported methods have been summarized.2. The first iodine/water-mediated deprotective oxidation of allyl benzyl ether toa,b-unsaturated ketone and aldehyde was reported.After conditional screening,1.6equivalents of iodine element in 1,4-dioxane/water?5:1?at reflux temperature for 24hours was the optimal reaction condition.In this condition,91%yield can be obtained,substrate's adaptability was good.Then this reaction system was applied to the conversion of alkane ethers,silyl ethers and allyl esters toa,b-unsaturated ketone.Allyl silyl ethers's transformation also showed excellent yield?allyltriethysilyl ether can obtain 95%yield?,a moderate yield?47%-68%?was obtained with alkane ethers and allyl esters.We had explored the reaction mechanism with ¹⁸O-labeling experiment.Experiment shows that the oxygen atom in the carbonyl group originated from H₂¹⁸O instead of the starting ether.The system of iodine-water-mediated deprotective oxidation of allylic ethers toa,b-unsaturated ketones and aldehydes is efficient and gentle.This system conforms the economy of steps,and damage few to environment.So this system has great application value.