Ethers monotosylates

Diols or (3-hydroxy ethers are particularly useful substrates for fragmentation. If the diol or hydroxy ether is converted to a monotosylate, the remaining oxy group can promote fragmentation. 

Bouzide, A. Sauve, G. Silver(I) oxide mediated highly selective monotosylation of symmetrical diols. Application to the synthesis of poly-substituted cyclic ethers. Org. Lett. 2002, 4, 2329-2332. 

Cerium(IV) ammonium nitrate in aqueous acetonitrile is an alternative oxidant for the cleavage of p-methoxybenzyl ethers.335 Compared with DDQ, it is seldom used336 337 but there are circumstances where it will work when DDQ fails. A case in point is shown in Scheme 4.182.338 The ditosylate 182.1 underwent oxidative hydrolysis in the usual way with DDQ to give the alcohol 18U in 80% yield but attempts to deprotect the monotosylate 182.3 failed under the same conditions. However, with CAN, the monotosylate gave the desired diol 182.4 in 30% yield together with the p-methoxybenzoate 1825 in 24% yield. 

Tosylation of dihydrolyoorine aiforded a monotosylate (L) which was converted to the epoxide (LI) with methanolic potassium hydroxide. Some 2-methyl ether (LII) was formed concurrently. The epoxide could... 

Selective monotosylations of symmetrical diols have been accomplished in good yields (75-93%) with a stoichiometric amount of tosyl chloride in the presence of Ag(I) oxide and a catalytic amount of potassium iodide. When excess Ag(I) oxide is used, polysubstituted cyclic ethers are formed in 61-88% yield. This method was also used for the synthesis of substituted crown ethers. 

Cyclic ethers from diol monotosylates 236. HOv. ..CH2CH2OTS... 

Selective monotosylation of symmetric diols was also reported. i This technique was further applied to the s)mthesis of cyclic ethers (eq 22). This process, performed in the presence of at least 3 equiv of Ag20, was particularly favorable when steri-cally undemanding five- or six-membered rings could be formed. However, the technique was also used for the formation of the three-membered oxirane ring and of a substituted 5-0-crown ether. 

A soln. of 3-desoxy-D-chitaric acid dimethylamide 6-monotosylate in ahs. tetra-hydrofuran added at —15 to a soln. of LiAlH4 in ahs. ether, heated rapidly to boiling at 45-46 with vibration, and refluxed 15 min. (-f-)-normuscarin. Y 65-70%.—A longer reaction time lowers the yield. F. amide reduction s. E. Hardegger, H. Furter, and J. Kiss, Helv. 41, 2401 (1958). 

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