87512-59-2Relevant academic research and scientific papers
Substitution and Elimination Reactions of 3- and 4-Alkyl-2H-1-benzopyrans with Organoaluminium and Organomagnesium Reagents
Alberola, Angel,Ortega, Alfonso Gonzalez,Pedrosa, Rafael,Bragado, Jose Luis Perez,Vicente, Martina
, p. 1259 - 1262 (2007/10/02)
2,3-Dialkyl- and 2,2,3-trialkyl-2H-1-benzopyrans react with triethylaluminium or ethylmagnesium bromide yielding substituted o-allylphenols in good yield.The reactions of 2,3-dialkyl-2H-1-benzopyrans are stereoselective.Either the E or Z isomers can be formed preferentially depending upon the experimental conditions; the stereoselectivity increases with the bulk of the alkyl substituent at C-3.However 2,4-dialkyl- and 2,2,4-trialkyl-2H-1-benzopyrans lead to o-allylphenols only with ethylmagnesium bromide; the mixture of E and Z isomers thus formed was found to be very difficult to separate.
The Behaviour of 2H-1-Benzopyrans Toward Trialkylaluminium Reagents
Alberola, Angel,Ortega, Alfonso Gonzalez,Pedrosa, Rafael,Bragado, Jose L. Perez,Amo, Justo F. Rodriguez
, p. 1209 - 1212 (2007/10/02)
2H-1-Benzopyrans react with trialkylaluminium compounds by alkyl- and hydrogen-transfer to C-2 and C-4 to give the o-allylphenols (2), (3), and the (E)-o-propenylphenols (4) and (5).The site of attack and the ratio of alkyl- to hydrogen-transfer depend on the alkylaluminium used and on the size of the substituent at C-2 of the pyran.A mechanism involving reaction of the alkylaluminium with the quinone methanide (6), which is in equilibrium with the pyran (1), is in accord with all experimental results.
