ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
2-(1′-Arylallyl)-phenols (9, 10, 11, 12, 13, 14, 15, 16) are transformed on heating in N, N-diethylaniline at 225° into trans-2-aryl-3-methyl-coumarans (26, 29, 32, 34, 36, 38, 40, 42) in excellent yields. The corresponding cis-coumarans are minor products. Similar thermal behaviour is shown by 2-(1′-vinylallyl)-phenols (7, 8) which are thermally converted into trans-3-methyl-2-vinyl-coumarans (24, 19) and 5-methyl-2,5-dihydro-(1-benzoxepins) (25, 18). The latter compounds are thermally unstable and rearrange to give approximatively 3:1 mixtures of trans- and cis-3-methyl-2-vinyl-coumarans (24, 19). Reaction mechanisms for these new thermal rearrangements are discussed in schemes 2, 3 and 4.The 2-(1′-arylallyl)-phenols 9, 12 and 14 yield under acidic conditions (HBr/HOAc) the expected 3-aryl-2-methyl-coumarans 28, 35, 39 along with 2-aryl-3-methyl-coumarans 26, 34, 38 and 2-aryl-2-methyl-coumarans 44, 45, 46. The intervention of phenonium ions is discussed for these reactions (cf. scheme 5).When the 2-(1′-arylallyl)-phenols 12 and 14 were irradiated in benzene solution with a mercury high pressure lamp, the main products obtained were 3-aryl-2-methyl-coumarans 35 and 39 which were formed rapidly. 2-Aryl-3-methyl-coumarans yield also 3-aryl-2-methyl-coumarans, when irradiated in benzene solution.
Additional Material:
11 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19720550526
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