Oxiranyl ethers

Hydroxymethyloxetanes 25 have been obtained stereoselectively fiom suitably substituted oxiranyl ethers 24 by the action of a mixture of LDA and potassium rert-butoxide. The relative stereochemistry of R and the hydroxymethyl group is determined by the stereochemistry in 24 but the relative stereochemistry of R and the alcohol group is produced in the reaction and was found always to be trans <01 JOC3201>. 

While allyl and glycidyl ethers are converted into a mixture of oxetane and oxepine products with xec-butyllithium, Mordini and co-workers reported that allyl, benzyl, and propargyl epoxy ethers can be regioselectively converted into 2-vinyl, 2-phenyl, or 2-aIkynyl-3-(hydroxyalkyl) oxetanes upon treatment with either Schlosser s base or other mixed metal bases. Some of the best results were obtained with the LDA/potassium ferf-butoxide mixture (LIDAKOR, ref 194). While rearrangement of propargylic or benzylic epoxide ethers formed exclusively the four-membered oxetanes, rearrangements of allyl oxiranyl ethers show a selectivity for cyclization to the seven-membered ring. Trialkylsilyl-substituted epoxide allyl ethers also show a preference for the oxepine, and mixtures are obtained as the size of the silyl substituents is increased (Scheme 17). 

The high reactivity of the two oxiranyl phenyl ethers accounts for the observed cytotoxicity, since they readily formed adducts with DNA further, the tl/2 values corresponding to mutagenicity matched the chemical half-lives [145],... 

Tricyclic oxiranyl-substituted cyclobutanone 7 rearranged quantitatively to bicyclic tetrahy-drooxepin 8 on treatment with boron trifluoride-diethyl ether complex in chloroform.225... 

Because of the special structural requirements of the resin-bound substrate, this type of cleavage reaction lacks general applicability. Some of the few examples that have been reported are listed in Table 3.19. Lactones have also been obtained by acid-catalyzed lactonization of resin-bound 4-hydroxy or 3-oxiranyl carboxylic acids [399]. Treatment of polystyrene-bound cyclic acetals with Jones reagent also leads to the release of lactones into solution (Entry 5, Table 3.19). Resin-bound benzylic aryl or alkyl carbonates have been converted into esters by treatment with acyl halides and Lewis acids (Entry 6, Table 3.19). Similarly, alcohols bound to insoluble supports as benzyl ethers can be cleaved from the support and simultaneously converted into esters by treatment with acyl halides [400]. Esters have also been prepared by treatment of carboxylic acids with an excess of polystyrene-bound triazenes here, diazo-nium salts are released into solution, which serve to O-alkylate the acid (Entry 7, Table 3.19). This strategy can also be used to prepare sulfonates [401]. 

In the case of nonsymmetrical epoxides, the regioselectivity is determined by the particular reaction conditions. Thus, styrene oxide (6) undergoes methanolysis in the presence of the Lewis acid catalyst copper(II) tetrafluoroborate to give the hydroxy ether 60, derived from attack of the nucleophile at the more substituted oxiranyl carbon. Similar outcomes have been observed in the solvolysis of 6 with the assistance of aminopropyl silica gel (APSG) supported iodine in catalytic quantities <02SL1251>. This selectivity appears to be much less decisive, however, in the case of monoalkyl epoxides, as illustrated in the corresponding reaction of 1-octene oxide (61), which yields an almost 1 1-mixture of isomers under the same conditions <02OL2817>. 

Glycide Glycidyl alcohol 3-Hydroxy-1,2-epoxypropane Methanol, oxiranyl- Oxiranemethanol Classification Epoxides Empirical C3H6O2 Formula OCH2CHCH2OH Properties Colorless liq. sol. in water, alcohol, and ether m.w. 74.09 dens. 1.12 b.p. 162 C ref. index 1.4330... 

Methyl-2-oxiranyl)-l, 4-benzenediol 4-Me ether, 1-angeloyl, in M-30098 Plicatin A, in D-10311... 

Hydroxy-1 (10),4,7( 11 )-germacratrien-12,8-olid-15-oic acid, H-30139 2-(3-Methyl-2-oxiranyl)-1,4-benzenediol 1 -O-(2,3-Epoxy-2-methylbutanoyl), 4-Me ether, in M-30098... 

A stereoselective approach to tetrasubstituted (Z)-/3-hydroxy-o -TMS (trimethylsi-lyl)enol ethers occurs via a sequential addition/[ 1,2]-Brook rearrangement/epoxide-opening process of TMS-substituted oxiranyl anions with acylsilanes (Scheme 46). ... 

A stereoselective approach to tetrasubstituted (ii)-/ -hydroxy silyl enol ethers from aryl-substituted oxiranyl anions and acylsilanes is reported to occur via a sequential addition - [l,2]-Brook rearrangement - epoxide-opening (Scheme 87). ... 

Scheme 4.25 Gold-catalyzed ring expansion of cw-l-oxiranyl-l-aUcynylcyclopropanes to eight-membered cyclic enol ether.

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