Biomedical subjects

Robert J Hinkle

Publications and source records attributed to Robert J Hinkle.

4 recordsLinked to original sources

PubMed2006

BiBr3-initiated tandem addition/silyl-Prins reactions to 2,6-disubstituted dihydropyrans.

A tandem addition/silyl-Prins reaction efficiently affords cis-2,6-disubstituted dihydropyrans (DHPs) using 5 mol % of BiBr3 in CH2Cl2. The reaction occurs between delta-triethylsilyloxyvinyltrimethylsilanes and a variety of aldehydes to give good to excellent isolated yields of DHPs. The diastereoselectivities in the crude products are significantly affected by aldehyde substitution with electron-rich aldehydes, providing 2-3:1 (cis:trans) and neutral (or electron-poor) aldehydes affording dr > or = 19:1 (cis:trans).

Journal Article↗

PubMed2003

Stereoselective construction of cyclic ethers using a tandem two-component etherification: elucidation of the role of bismuth tribromide.

The stereodivergent construction of cyclic ethers remains an important area of synthetic interest, particularly given the ubiquity of C-glycoside derivatives in natural and unnatural pharmacologically important agents. This work describes a series of intramolecular etherification reactions of delta-trialkylsilyloxy aldehydes and ketones using catalytic bismuth tribromide and various trialkylsilyl nucleophiles for the construction of cis- and trans-2,6-di- and trisubstituted tetrahydropyrans. Furthermore, this study provides compelling evidence for the fact that the catalysis may be attributed to the hydrogen bromide and bismuth oxybromide derived from the hydrolysis of bismuth tribromide. The synthetic utility of this protocol is highlighted in the ability to construct adjacent tertiary ethers in a highly stereoselective manner and the development of a sequential two-component cross-coupling followed by reductive etherification process for the expeditious synthesis of nonadjacent tetrahydropyran rings.

Bismuth↗

PubMed2002

Structural and electronic characteristics of thienyl(aryl)iodonium triflates.

A general strategy toward the synthesis of aryliodonium triflate salts has been exploited to afford derivatives that incorporate thiophene and bithiophene components. Both mono- and bis(iodonium) salts have been realized, and a series of bithienyl(aryl)iodonium triflates with increasingly electron-withdrawing substituents on the aryl moiety have been synthesized. X-ray crystallographic analysis of four derivatives (4a, 4b, 6b, and 8c) demonstrates that the solid-state organization of these salts incorporates extensive networks of secondary bonding interactions between the cationic iodonium centers and the triflate counterions. UV-vis spectroscopic analysis shows that the electronic interactions between pendent aryl and heteroaryl groups across the iodonium center can be dictated by substitution. Furthermore, the energy of the HOMO-LUMO gap decreases substantially in weakly or noncoordinating solvents.

Journal Article↗

PubMed2002

(Z)-2-Methylbuten-1-yl(aryl)iodonium trifluoromethanesulfonates containing electron-withdrawing groups on the aryl moiety.

The crystal structures of [(Z)-2-methylbut-1-en-1-yl][4-(trifluoromethyl)phenyl]iodonium trifluoromethanesulfonate, C(12)H(13)F(3)I(+).CF(3)O(3)S(-), (I), (3,5-dichlorophenyl)[(Z)-2-methylbut-1-en-1-yl]iodonium trifluoromethanesulfonate, C(11)H(12)Cl(2)I(+).CF(3)O(3)S(-), (II), and bis[[3,5-bis(trifluoromethyl)phenyl][(Z)-2-methylbut-1-en-1-yl]iodonium] bis(trifluoromethanesulfonate) dichloromethane solvate, 2C(13)H(12)F(6)I(+).2CF(3)O(3)S(-).CH(2)Cl(2), (III), are described. Neither simple acyclic beta,beta-dialkyl-substituted alkenyl(aryl)idonium salts nor a series containing electron-deficient aryl rings have been described prior to this work. Compounds (I)-(III) were found to have distorted square-planar geometries, with each I atom interacting with two trifluoromethanesulfonate counter-ions.

Journal Article↗