Convenient syntheses of fluorous phenols of the formula HOC6H5−n((CH2)3(CF2)7CF3)n (n=1, 2) and the corresponding triarylphosphites
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The aldehydic benzyl ethers PhCH2OC6H4CHO (2; a/b = paralmeta series) are readily available from the corresponding phenols and react with Wittig reagents derived from [Ph3PCH2CH2Rf8]+- (Rf8 = (CF2)7CF3) to give PhCH2OC6H4CH=CHCH2Rf8 (86-93%, Z major). Reactions with H2 over Pd/C give the fluorous phenols HOC6H4(CH2)3Rf8 (4a,b; 87-91%). Condensations with PCl3 and NEt3 (3.0:1:0:3.3 mol ratio) give the flourous phosphites P[OC6H4(CH2)3Rf8] 3 (5a,b; 92-94%), but traces of 4a,b are difficult to remove. The phthalate-based benzyl ethers PhCH2OC6H3COOR 2 (7; c/d = 3,5/3,4 -OC6H3-3,n-(R)2 series) are easily accessed and reduced with LiAlH4 to the diols PhCH2OC6H3(CH2OH)2 (8c,d; 89-90%). Diol 8c and the Dess-Martin periodinane react to give the dialdehyde PhCH2OC6H3(CHO)2 (9C; 95%). This is elaborated by a sequence analogous to 2 → 4 → 5 to the flourous phenol HOC6H3((CH2)3Rf8) 2 (11c; 97%/96%, two steps) and phosphite P[OC6H3((CH2)3Rf8) 2]3 (12C, 92%), from which traces of 11c are difficult to remove. Diol 8d can be similarly elaborated to 11d, but the dialdehyde 9d is labile and combined yield of the Dess-Martin/Wittig steps is 32%. The CF3C6F11/ toluene partition coefficients of 11c,d, and 12c (two pony tails; 70:30,72:28, 92:8) are much higher than those of 4a and b (one pony tail; 12:88, 14:86). © 2002 Elsevier Science B.V. All rights reserved.
author list (cited authors)
Le Stang, S., Meier, R., Rocaboy, C., & Gladysz, J. A.