Organic Lab Reactions 20

Organic Lab Reactions 20 - by the |8-carbon followed by...

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SIDE REACTIONS 15 1,3-pentadiene and ethyl 4-hydroxybenzoate. 62 2-Cyclohexenyl phenyl ether (LII) gives a 50-60% yield of phenol and cyclohexadiene, with 5% of the expected rearrangement product (LIII) and 15% of hexahydrodi- benzofuran (LIV). 63 The very highly substituted ether, a,a,7,7-tetra- LIV methylallyl phenyl ether (LV) undergoes only the cleavage reaction without any rearrangement, 33% of the diene being obtained after one hour at 160-170 0 . 61 It has been reported, 36 ' M but without experimental details, that 7,7-dimethylallyl phenyl ether yields phenol and isoprene on heating, but that when heated with sodium carbonate it undergoes rear- rangement. Recently it has been shown 640 that pyrolysis of 7,7- dimethylallyl 4-carbethoxyphenyl ether (LVo) gives OCH 2 CH=C(CH 3 ) 2 (CH 3 ) 2 HCH S COOC2H5 LVo LV6 mainly the cleavage products, isoprene and ethyl 4-hydroxybenzoate; the dihydrobenzofuran derivative (LVb) is produced in small yield, apparently as the result of an abnormal rearrangement with attachment
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Unformatted text preview: by the |8-carbon, followed by ring closure. The cleavage of a substituted allyl ether and formation of the phenol have been observed also in an attempted catalytic reduction at low temperature and pressure with a palladium 6 or a platinum catalyst. 66-18 The other side reaction which is sometimes troublesome is illustrated by the formation of LIV (see p. 18). The rearrangement of allyl phenyl ether itself yields, in addition to 2-allylphenol,* a small amount (4-6%) of the methyldihydrobenzofuran (LVI), which is probably produced 7 N LVI * See p. 79 of the article cited in reference 11. 6a Lauer and Ungnade^ J. Am. Chem. Soc., 61, 3047 (1939). ea Cornforth, Hughes, and Lions, J. Proc. Royal Soc. N. S. Wales, 71, 323 (1938) [C. A •33, 148 (1939)]. M Claisen, J. prakt. Chem., [2] 105, 65 (1922). Mo Lauer and Moe, J. Am. Chem. Soc, 65, 289 (1943). 66 Tarbell and Wilson, unpublished observation....
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