Ronald Charles David Breslow (March 14, 1931 – October 25, 2017) was an American chemist from Rahway, New Jersey. He was University Professor at Columbia University, where he was based in the Department of Chemistry and affiliated with the Departments of Biological Sciences and Pharmacology; he had also been on the faculty of its Department of Chemical Engineering. He had taught at Columbia since 1956 and was a former chair of the university's chemistry department.
Life and career
Breslow was born in Rahway, New Jersey, the son of Gladys (Fellows) and Alexander E. Breslow. He was interested in the design and synthesis of new molecules with interesting properties, and the study of these properties. Examples include the cyclopropenyl cation, the simplest aromatic system and the first aromatic compound prepared with other than six electrons in a ring. His seminal contributions include the correct site of reactivity of thiamin diphosphate in enzymes that promote the decarboxylation of pyruvate – based on his pioneering use of proton NMR with small molecule analogues – and the rate enhancement provided by binding to cyclodextrins produced major themes for study in modern organic and biological chemistry. He also co-discovered the histone deacetylase inhibitor SAHA (Vorinostat) which is FDA-approved for the treatment of cutaneous T-cell lymphoma. Breslow earned his B.A., M.A. and Ph.D. from Harvard University, where his doctoral advisor was R. B. Woodward. Among Breslow's former Ph.D. students is Robert Grubbs, who won the Nobel Prize in Chemistry in 2005, and Doug La Follette, Secretary of State of Wisconsin. Robert Lefkowitz, who won the Nobel Prize in Chemistry in 2012, studied under Breslow as an undergraduate. Breslow received many honors and awards, including the National Medal of Science in 1991, the Welch Award, the Arthur C. Cope Award (1987), the NAS Award in Chemical Sciences, the American Chemical Society's ACS Award in Pure Chemistry (1966), the Othmer Gold Medal (2006), the Priestley Medal (1999), and the 2014 American Institute of Chemists (AIC) Gold Medal. In recognition of his classroom skills, Columbia awarded him both its Mark Van Doren Award and its Great Teacher Award. He served as president of the ACS in 1996 and chaired the chemistry division of the National Academy of Sciences from 1974 to 1977. In 1997 he was named one of the top 75 contributors to the chemical enterprise of the past 75 years by Chemical & Engineering News. He was the Myron L. Bender distinguished lecturer at Northwestern University in 1999. The Ronald Breslow Award for Achievement in Biomimetic Chemistry, awarded annually by the ACS, is named in his honor. He was a member of the National Academy of Sciences, the American Academy of Arts and Sciences, the European Academy of Sciences, and the American Philosophical Society. He is also a foreign member of the Royal Society and an honorary member of many other scientific bodies around the world. In 2012, his paper "Evidence for the Likely Origin of Homochirality in Amino Acids, Sugars, and Nucleosides on Prebiotic Earth" was retracted from the Journal of the American Chemical Society due to copyright concerns, leading to a debate on self-plagiarism and the distinction between a personal review and a paper.
Synthesis of cyclopropenyl cation
This cation was first prepared by mixing 3-chlorocyclopropene with antimony pentachloride, aluminum trichloride, or silver tetrafluoroborate. Carbon-13 NMR shows singlets with a JC–H coupling constant of 265 ± 1 Hz. The authors suggest that this coupling constant is suggestive that the C–H bond is 53% s character. The overall bonding framework then consists of sp orbitals to all hydrogens, two sp3 orbitals for each sigma bond, and one p orbital for the π framework.
D-orbital conjugation It had been suggested that carbanion-sulfone double bonds will not show aromatic character-primarily as a result of the nodes present in d-orbitals. Straight chain analogs were chosen based on the comparable acidity, combined with previous studies indicating that steric effects are largely negligible. The straight chain analogs are shown below.
Compound II was treated with dimethoxyethane / D2O / triethylamine and was found to be completely deuterated upon recovery. The deuterated compound was then treated with butyllithium in ether, with dimethoxyethane and 2N HCl regenerating the starting material. The cyclic analog (III, shown below) was deuterated in the same manner, and addition of deuterated I, followed by quenching to regenerate the protonated form, was analyzed by NMR. There was one proton peak, and it was shown to equilibrate equally between compounds II and III, indicating that compounds had similar acidity. From this result, the researchers concluded that compound III was not aromatic, because stabilizing effect of aromaticity on the anion should increase the acidity of the parent compound.
The ester analogs were prepared (IV and V) and were found to be acidic enough for titration. The compounds were titrated under nitrogen with 0.2N NaOH with a Beckman Model GS meter with an E-2 electrode. Compound IV was found to have a pKa of 8.9 ± 0.1, while compound V had a pKa of 11.1 ± 0.2.
… excerpt ends here. Continue reading the full article.
