Allyl ethers oxirane ring opening

Selected examples of ring-opening of oxiranes by chloroalkanes to yield allyl ethers... 

All the allylic alcohols form the oxirane as the initial product, but as the conversion increases the ring opened products, the ether diols (formed by reaction with the alcohol solvent) and the triol (formed by reaction with water) are also observed. It is apparent that cis-crotyl alcohol reacts approximately three times more rapidly than the trans-crotyl even though it is present as the minor component. This was inve.stigated further using crotyl alcohols with a range of trans/cis ratios and the results are shown in Table 1. 

Starting materials, like 141, which are accessible from alkenes by azido-selenenylation, afforded only in a few cases vinyl azides exclusively as shown by the example 141 142 (Scheme 5.19). In most cases, after oxidation of the vicinal phenylseleno azides and elimination reaction on the intermediate selenoxide, mixtures of allyl and vinyl azides were obtained. Ring opening of trialkylsilyl-substituted epoxides was utilized several times for stereoselective synthesis of vinyl azides. Thus, treatment of the frani -contigured oxiranes 143 with azidotrimethylsilane and boron trifluoride etherate yielded cis-conflgured products 145. This result was explained by the intermediate 144 which should undergo anti-elimination. On the other hand, when subjected to sodium azide in dimethylformamide, epoxides 146 were transformed into vinyl azides 148 via... 

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