Epoxide synthesis diazomethane

The ability of diazomethane to replace hydrogen atoms in "iodic compounds like carboxylic adds, phenolB, and enolB has long been known. Although thw aspect need not be dealt with extensively h tv. it should be stressed that with a polyfunctional substrate diazomethauc can function at several reaction sites. Some discrimination therefore necessary in selecting this reagent for epoxide synthesis. 

An important exception to the applicability of diazomethane for epoxide synthesis will be apparent when it is recalled that this ivugoni is exceedingly potent in replacing acidic hydrogens in enoJs.-1 1 ... 

Spiro epoxides are also valuable intermediates for the synthesis of type I branched-chain sugars. These spiro epoxides are formed from ketosugars using diazomethane addition or sulfonium chemistry. Further ring opening of the epoxide allows the introduction of various nucleophiles [1], Chloro spiroepoxide 15 (Scheme 9) has been prepared recently from ketosugar 1 dichloromethyllithium [28]. 

Scope. Epoxides have been prepared from a wide variety ot carbonyl compounds by diazomethane synthesis, in yields ranging freon a few percent to nearly quantitative. No attempt will be made here to present a complete catalogue of reactions, inasmuch as this has been done elsewhere.4 6-463 A few additional examples have appeared since then, which are included in the present text. Reference... 

A convenient synthesis of epoxide 38 was developed using commercially available Boc-protected phenylalanine.38 As shown in Scheme 11, protected phenylalanine 44 was converted to alcohol 45 in a three-step sequence, involving (1) reaction of 44 with isobutyl chloroformate followed by diazomethane to give the corresponding diazoketone, (2) treatment of the diazoketone with HCI to provide the corresponding chloroketone, and (3) reduction of the resulting ketone with NaBH4 to provide 45 in 52% overall yield. Treatment of 45 with alcoholic KOH furnished epoxide 38 in 99% yield. 

The ether linkage ( C—0—C ) is normally prepared by one of the three following procedures. The Williamson synthesis is the most general method, while the diazomethane procedure and the epoxide formation procedure are useful for specific types of... 

The g.l.c. separation of cis- and /m/w-epoxy-esters forms the basis of a new procedure for determining the proportion of cis- and tra/w-isomers in a mixture. The report that w-chloroperbenzoic acid can be used at 90 without decomposition in the presence of suitable radical inhibitors may be of value when epoxidizing alkenes of reduced reactivity. Several fluorostearic acids have been prepared by interaction of mesyloxy-acids with tetrabutyl-ammonium fluoride in acetonitrile. A procedure for methylation (by diazomethane in the presence of boron trifluoride) and demethylation (by reaction with sodium borohydride and iodine, followed by methanol), with retention of optical activity, could prove useful in the synthesis of compounds of known configuration. ... 

Many of the steps involved manipulation of protecting groups, but the major transformations were a) addition of diazomethane to a 1-ulose to give a mixture of epoxide (36) and its C-1 epimer b) demethylatlon at 0-2 c) formation of epoxides (37) by sulphonate displacement d) synthesis of alkene (38) by conversion of these epoxides to lodohydrlns and elimination (POCl -py) and e) displacement of an allylic hydroxy group by azide using the DEAD-TPP reagent... 

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