Allyl glycidyl ether cyclization

Tetrahydrooxepinols are formed in moderate yields on cyclization of carbanions formed from allyl glycidyl ethers the process competes with the formation of isomeric (vinyloxetanyl)carbinols <88CC625,90TL350l>. The mechanism has been rationalized as shown in Scheme 24. 

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). 

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See also in sourсe #XX -- [ , , ]

See also in sourсe #XX -- [ , , ]

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