53713-29-4Relevant academic research and scientific papers
Lewis Acid Mediated Nucleophilic Substitution Reactions of 2-Alkoxy-3,4-dihydro-2H-1-benzopyrans: Regiochemistry and Utility in the Synthesis of 3,4-Dihydro-2H-1-benzopyran-2-carboxylic Acids
Cohen, Noal,Schaer, Beatrice,Saucy, Gabriel,Borer, Rene,Todaro, Louis,Chiu, Anne-Marie
, p. 3282 - 3292 (2007/10/02)
The Lewis acid mediated nucleophilic substitution reactions of a variety of 2-alkoxy-, 2-hydroxy-, and 2-(acyloxy)-3,4-dihydro-2H-1-benzopyrans (chromans) have been studied within the context of developing new synthetic routes to chroman-2-carboxylic acids, certain of which have utility as antioxidants and drug intermediates.The scope and limitations of these transformations have been determined.Treatment of 2-methoxychromans in the α-tocopherol structural class (9, 25) with cyanotrimethylsilane in the presence of TiCl4 or BF3 etherate generally leads in good yield to the desired 2-cyanochromans 10 and 26.On the other hand, ketals of the type 19 react less efficiently, giving poor to moderate yields of the cyanochromans 36 along with regioisomeric products (37, 38).Spiro-fused ketals such as 28 exhibit dichotomous behavior dependent on the Lewis acid employed, while the pyranochroman 34b affords 35 in good yield.Thus the regioselectivity of these processes appears to be highly dependent on substrate structure and the nature of the Lewis acid.
Preparation of chromane derivatives
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, (2008/06/13)
Chromane derivatives (I) STR1 where R1, R2 and R3 are H or C1 -C8 -alkyl, R4 is H, C1 -C8 -alkyl or C1 -C8 -acyl and R5 is C1 -C8 -alkyl are prepared by reacting a hydroquinone (II) STR2 with a Lewis acid or a Lewis acid derivative having the same action, and with a nitrile CH2 =CH--C(R5)(OR6)CN (III), where R6 is H, C1 -C4 -acyl or C1 -C4 -alkyl, or with a compound from which III is formed in situ, in the presence of an inert solvent.
