UNSPECIFIED. (2004) Parallel synthesis and study of fluorous biphasic partition coefficients of 1H,1H,2H,2H-perfluoroalkylsilyl derivatives of triphenylphosphine: A statistical approach. JOURNAL OF COMBINATORIAL CHEMISTRY, 6 (3). pp. 363-374. ISSN 1520-4766

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Abstract

A library of fluorous, (1H,1H,2H,2H-perfluoroalkyl)silyl-substituted derivatives of triphenylphosphine, Ph3-aP[C6H5-y{SiMe3-b(CH2CH2CxF2x+1)(b)}(y)-pos](a) [a = 1-3; b = 1-3; x = 4, 6, 8, or 10; pos = 3, 4 (y = 1) or 3,5 (y = 2)], was prepared using parallel synthetic techniques. Upon variation of these four parameters, a total of 108 different fluorous phosphines can be synthesized. Using factorial design, 37 phosphines were selected and their partition coefficients in the typical fluorous biphasic solvent system PFMCH/toluene (PFMCH = perfluoromethylcyclohexane) determined. By fitting of the partition coefficient data to linear functions of the parameters a, b, and x, the partition coefficients of the remaining 71 fluorous phosphines, which were not prepared, could be predicted. Using this approach, some unexpected trends in the dependence of the partition coefficient on variations of the four parameters became clear, resulting in a better understanding of the optimum fluorous substitution pattern for obtaining the highest partition coefficient (P). In this way, the partition coefficient was increased by 2 orders of magnitude, i.e., from the initial value P = 7.8 for 1(3, 2, 6, C4) to P > 238 for 1(2, 3, 6, C3C5). Para- and 3,5-substituted phosphines showed irregular behavior in the sense that elongation or increase of the number of perfluoroalkyl tails did not necessarily lead to higher partition coefficients. Particularly high values were found for phosphines containing a total of 72 fluorinated carbon atoms on the meta position(s) of the aryl rings. Linear relationships were found between the predicted log P of I(a, b, x, C4) and the experimentally determined log P values of fluorous diphosphines [CH2P{C6H4(SiMe3-b(CH2CH2C6F13)(b))-4}(2)](2) and monophosphines Ph3-aP(C6H4(CH2CH2C6F13)-4)(a). One of the most fluorophilic phosphines, i.e., 1(3, 1, 8, C3C5), was applied and efficiently recycled in rhodium-catalyzed, fluorous hydrosilylation of 1-hexene by HSiMe2Ph using PFMCH as the fluorous phase and the substrates as the organic phase. It was demonstrated that a higher partition coefficient of the ligand in PFMCH/toluene at 0 degreesC indeed resulted in less leaching of both the catalyst and the free ligand during phase separation.

Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry
Journal or Publication Title:	JOURNAL OF COMBINATORIAL CHEMISTRY
Publisher:	AMER CHEMICAL SOC
ISSN:	1520-4766
Date:	May 2004
Volume:	6
Number:	3
Number of Pages:	12
Page Range:	pp. 363-374
Identification Number:	10.1021/cc049959z
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/8415

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