Organic syntheses on an icosahedral borane surface: closomer structures with twelvefold functionality.
The syntheses of a series of novel ester-linked derivatives of the icosahedral [closo-B12(OH)12]2- boron cluster (closomer esters) are described using several synthetic methods. The reaction of bis(tetrabutylammonium)-closo-dodecahydroxy-dodecaborate, [NBu4]2 1, with carboxylic acid chlorides and anhydrides, vinyl esters with a Y5(OiPr)13O catalyst and 1,1'-carbonyldiimidazole-activated carboxylic acids yields the corresponding dianionic dodeca-ester closomers. The method using 1,1'-carbonyldiimidazole-activated carboxylic acids may be employed as a general synthetic strategy. The use of elevated reaction temperatures, achievable under pressure, to expedite syntheses is described. An attractive methodology using immobilized scavenger reagents for the expeditious purification of the closomer esters was employed. The developed methodology is compatible with a variety of peripheral functional groups attached to the termini of densely packed, carboxylate ester-linked radial arms bonded to the icosahedral borane surface. A closomer ester having twelve terminal amino groups was prepared, and without isolation, fully acetylated in good yield.
Li
Tiejun
T
Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive East, Los Angeles, California 90095, USA.
Jalisatgi
Satish S
SS
Bayer
Michael J
MJ
Maderna
Andreas
A
Khan
Saeed I
SI
Hawthorne
M Frederick
MF
D000215:Acylation; D000818:Animals; D001880:Boranes / Q000138:chemical synthesis* / Q000737:chemistry / Q000493:pharmacokinetics; D001896:Boron Compounds / Q000737:chemistry; D002264:Carboxylic Acids / Q000737:chemistry; D004952:Esters / Q000737:chemistry / Q000493:pharmacokinetics; D007093:Imidazoles / Q000737:chemistry; D051379:Mice; D008807:Mice, Inbred BALB C; D008958:Models, Molecular; D008968:Molecular Conformation; D014018:Tissue Distribution
D001880:Boranes; D001896:Boron Compounds; D002264:Carboxylic Acids; D004952:Esters; D007093:Imidazoles; C119788:dodecaborate