This paper in discussion describes the selective removal of a methoxy protection group adjacent to a hydroxy functional group using Diacetoxy iodobenzene and iodine. As many of you know eugenol and vanillin fit the bill for this nicely. Now even though the whole process discribed follows a one pot synthesis to form a methylenedioxy bridge follwed by subsequent hydrolysis using Potassium hydroxide. In the case of eugenol to safrole it is totaly unnessasary to perform this hydrolysis as our target compound is formed in the first step of the synthesis. Most if not all examples of this procedure utilize substrates with multiple methoxy functional grouping which in some cases leads to dimerization and complex of products but Eugenol at first glace,(ignoring the possibly problematic terminal double bounding),appears to be one of the simplest and best substrates for the use of this process. The reagents that are used in this synthesis may well be above the average chemist but I still want to post this procedure because it may possibly lead to an alternate route that is more within reach for most of us. This is the main chemical in question and it is called DIB in the paper. If anyone has any ideas on how to synthesis this chemical please share. [img]http://cyclicastrology.faithweb.com/images/chemistry/DIB.JPG[/img] I would assume that one should begin the synthesis with phenyl iodine but I could be wrong. Main problem that is proving it self to me is the understanding of the paper in question. The writter of this incohearent text seems to have less flare for writting papers then your truely and for those of you that know thats saying alot. I find this text to be highly confusing and the author spends to much time using abreviations without discriptions of what the compounds are. With that being said it does appear to be a total synthesis of the precursors and the the following reaction but this just leads to the confusion of the paper. I will post more on the procedure when I feel up to it but for the time being Im tired of writting. Without Further Adu here is the synthesis modifyed for the conversion of Eugenol. [size=18][b][u]Experimental One pot Eugenol conversion thru intermolecular hydrogen extraction[/b][/u][/size] [img]http://cyclicastrology.faithweb.com/images/chemistry/reaction.JPG[/img] A solution of 4 ml (anhy)Dichloromethane and 32.84 grams of Eugenol is mixed with 96.63 grams PhI(OAc)2 and 25.38 grams of iodine under inert atmosphere. Mixture is irradiated with two tungsten- filament lamps at 23*C for 1 hour. After reaction completion the mixture is added to a 10% sodium thiosulfate solution to remove free iodine and then extracted with two portions of Dichloromethane. Organics are dried with sodium sulfate and evaportated under vacuum to afford an unknown quantity and purity of MethyleneDioxy allybenzene. [b][u]Examples from literature [/b][/u] I must include this because I am not the greatest of chemist in the world and prone to errors in translation of millimoles so if anyone sees a mistake in the above procedure that has been modifyed for Eugenol [u][b]Method B:[/b][/u] A solution of the substrate 13 (0.2 mmol) in dry dichloromethane (4 mL) was treated with DIB (97 mg, 0.3 mmol) and iodine (51 mg, 0.2 mmol) under nitrogen. The reaction mixture was irradiated with two tungsten-filament lamps for 1 h at 22- °C. Then the solvent was evaporated under vacuum, and the residue was treated with 1 N NaOH (MeOH/H2O, 9:1, 0.5 mL). Workup and purification as in Method A afforded the diol 62 (50%). [b]Related reading for IHA reactions.[/b] Even though many links may not pertain to the above mentioned synthesis I have added these for extra reading so that a move available means of performing this reaction can be found. I will post more as I come across them. [b]Full text[/b] http://www.rsc.org/ej/P2/1997/a700948h.pdf http://article.pubs.nrc-cnrc.gc.ca/RPAS/rpv?hm=HInit&afpf=v90-260.pdf&journal=cjc&volume=68 http://turroserver.chem.columbia.edu/PDF_db/publications_501_550/525.pdf If anyone has access to any of these articals would you be kind enough to post them please. http://cat.inist.fr/?aModele=afficheN&cpsidt=19322821 http://sciencelinks.jp/j-east/article/199910/000019991099A0156433.php http://pubs.acs.org/doi/abs/10.1021/ja002301e 164.20 eugenol g/mol 164.20 * .001 * .2 = 0.9008 = .0328 322.10 32.84 grams of Eugenol 25.38 grams of Iodine. 96.63 grams DIB ================================================ After reading up on the mechanics some more I have come across some intresting things that pertain to the reaction that is being used and some possible alternatives to the procedure. The PhI(OAc)2 isnt the agent responsible for the reaction that is desired. The insitu formation of AcOI is though. The reaction procedes as such: [b] PhI(OAc)2 + I2 >> PhI + 2AcOI [/b] At first I thought that one could possibly make AcOI and use that until I found that it has never been isolated so must be pretty unstable. But I have also come across the old form of this double IHA reaction and it use to be performed with Lead(IV)acetate and Iodine and from what some of the papers that java sent me this may just well perform better for the reaction that is desired. When the reaction crude from a DIB reaction was treated with silver acetate in acetone the chemical yield of epoxide was notably increased. This could possibly work as well for LTA which already states greater then 80% yeilds with there substrate. Preperation of Lead(IV)acetate is a well understood and documented reaction from Lead tetra oxide and can be found here http://designer-drugs.com/pte/12.162.180.114/dcd/chemistry/lead.tetraacetate.html As this paper states there are other methods using electro chemistry to perform this reaction. Also possible is the formations of AcOI and found what appears to be a mixture of copper acetate/GAA/I2 with heat can form iodine-copper acetate. This compounds ability to perform the reaction in discussion is unknown to me at the time. The only down fall I can forsee with performing this reaction has nothing to do with fancy chemicals or hard to perform reactions but more to do with the fact that Iodine isnt exactly the easyest material to come by. But on a lighter note it is also not consumed so to speak in the reaction and recycling could be a great possibilty. [b][u]acetoxyl related material[/b][/u] Just a couple of papers I pulled up relating to the use and synthesis of acetoxyls http://www.journalarchive.jst.go.jp/jnlpdf.php?cdjournal=bcsj1926&cdvol=57&noissue=9&startpage=2691&lang=en&from=jnlabstract Synthesis using copper acetate discussed. http://ir.lib.u-ryukyu.ac.jp/bitstream/123456789/5372/1/No82p77.pdf ============================================================================================================== The lead tetra-acetate (LTA)- iodine procedure has been the most frequently used and appears to give the best yields. It produces alkoxyl radicals from alcohols when used in combination with Iodine. LTA is known to cause the secondary hydrogen abstraction on treatment of alcohols. When the reaction crude from a DIB reaction was treated with silver acetate in acetone the chemical yield of epoxide was notably increased. This could possibly work as well for LTA which already states greater then 80% yeilds. Had refrences: [b]Photochemistry of nitroso compounds in so1ution.l X. The reaction[/b] pattern of photo-excited nitrosamides http://article.pubs.nrc-cnrc.gc.ca/RPAS/rpv?hm=HInit&afpf=v69-398.pdf&journal=cjc&volume=47 Needed refrences: Abstract {REQUESTED SciMad} [b]Reactions with lead tetraacetate—IV *1, , *2: Oxidation of saturated aliphatic alcohols—II; Alcohols of low molecular weight [/b] The action of lead tetraacetate on ethanol, 1-propanol, 2-propanol and 2-butanol has been studied under various experimental conditions, and it was found that the tetravalent lead compound reacts with alcohols in ways not so far observed. The possible reaction schemes are discussed in terms of homolytic and heterolytic cleavage of the intermediate alkoxy lead acetate complexes. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6THR-42GF0P9-HV&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=62e9295943b58a395f20bcd6d872c587 [quote]The fact that the identity of reactive intermediates in the Fenton-reaction still is subject to debate17 illustrates the difficulties in separating oxygen radical chemistry from transformations by metal ion-based oxidants in those instances, where O-radicals are considered to be formed from alcohols,18 alkyl hydroperoxides,19 or hydrogen peroxide in the presence of metal ions[/quote] [quote] Due to its unpaired electron, an alkoxyl radical may combine with a second radical. However, dimerizations of alkoxyl radicals to afford dialkylperoxides is a synthetically inefficient reaction, since O-radical concentrations in solutions are often low.53 Usually other much faster elementary reactions interfere with the alkoxyl radical combination reaction.Thus, oxygen-centered radicals readily add to carbon-carbon38 or carbon-nitrogen bonds50 to afford intermediates which may either be trapped to give synthetically useful products or may undergo further radical reactions.[/quote] [quote] Alkoxyl radicals undergo homolytic substitutions. Due to relatively low C–H bond dissociation energies (see Table 1) and the large number of hydrogen atoms present in both organic compounds and solvents, the majority of homolytic substitutions are associated with hydrogen atom transfer reactions[/quote] [Img]homolytic substitutions[/img] [quote] Since competitive oxidations of functional groups, for example of C=C bonds, may interfere with the O-radical generation step, the use of type III-precursors in alkoxyl radical based syntheses is restricted.[/quote] [b]Source:[/b]Selectivity in the Chemistry of Oxygen-Centered Radicals PAGE 6