Jack D. Brown

Bio: Jack D. Brown is an academic researcher from Utah State University. The author has contributed to research in topics: Bicyclic molecule & Alkylation. The author has an hindex of 11, co-authored 15 publications receiving 625 citations.

ORTHO METALATION DIRECTED BY α-AMINO ALKOXIDES

Abstract: L'addition de dialkyl amidures de lithium sur des aldehydes aromatiques (naphtalenecarbaldehydes, benzaldehydes substitues) dans le THF ou le benzene, conduit a des hemiaminals qui sont lithies en position ortho par le butyl-lithium L'alkylation suivie de l'hydrolyse, des produits lithies fournit les arenals substitues en ortho

A highly stereocontrolled, four-step synthesis of (.+-.)-lasubine II

Abstract: Synthese a partir de R-MgBr, Z-Cl et methoxy-4 pyridine (Z=benzyloxycarbonyl et R=dimethoxy-3,4 phenyl) via la Z-1 R-2 dihydro-2,3 1H-pyridone-4 et la chloro-4' butyl-2 Z-1 R-6 piperidone-4

Ortho substitution of m-anisaldehyde via .alpha.-amino alkoxide directed lithiation

Abstract: Grâce aux amidures de lithium, la methylation de l'anisaldehyde a lieu selectivement en ortho

Thienoacene‐Based Organic Semiconductors

Abstract: Thienoacenes consist of fused thiophene rings in a ladder-type molecular structure and have been intensively studied as potential organic semiconductors for organic field-effect transistors (OFETs) in the last decade. They are reviewed here. Despite their simple and similar molecular structures, the hitherto reported properties of thienoacene-based OFETs are rather diverse. This Review focuses on four classes of thienoacenes, which are classified in terms of their chemical structures, and elucidates the molecular electronic structure of each class. The packing structures of thienoacenes and the thus-estimated solid-state electronic structures are correlated to their carrier transport properties in OFET devices. With this perspective of the molecular structures of thienoacenes and their carrier transport properties in OFET devices, the structure-property relationships in thienoacene-based organic semiconductors are discussed. The discussion provides insight into new molecular design strategies for the development of superior organic semiconductors.

Structure and Reactivity of Lithium Enolates. From Pinacolone to Selective C‐Alkylations of Peptides. Difficulties and Opportunities Afforded by Complex Structures

Abstract: The chemistry of lithium enolates is used to demonstrate that complex structures held together by noncovalent bonds (“supramolecules”) may dramatically influence the result of seemingly simple standard reactions of organic synthesis. Detailed structural data have been obtained by crystallographic investigations of numerous Li enolates and analogous derivatives. The most remarkable features of these structures are aggregation to give dimers, tetramers, and higher oligomers, complexation of the metal centers by solvent molecules and chelating ligands, and hydrogen-bond formation of weak acids such as secondary amines with the anionoid part of the enolates. The presence in nonpolar solvents of the same supramolecules has been established by NMR-spectroscopic, by osmometric, and by calorimetric measurements. The structures and the order of magnitude of the interactions have also been reproduced by ab-initio calculations. Most importantly, supramolecules may be product-forming species in synthetic reactions of Li enolates. A knowledge of the complex structures of Li enolates also improves our understanding of their reactivity. Thus, simple procedures have been developed to avoid complications caused by secondary amines, formed concomitantly with Li enolates by the common methods. Mixtures of achiral Li enolates and chiral Li amides can give rise to enantioselective reactions. Solubilization by LiX is observed, especially of multiply lithiated compounds. This effect is exploited for alkylations of N-methylglycine (sarcosine) CH2 groups in open-chain oligopeptides. Thus, the cyclic undecapeptide cyclosporine, a potent immunosuppressant, is converted into a THF-soluble hexalithio derivative (without epimerization of stereogenic centers) and alkylated by a variety of electrophiles in the presence of either excess lithiumdiisopropyl amide or of up to 30 equivalents of lithium chloride. Depending on the nature of the LiX additive, a new stereogenic center of (R) or (S) configuration is created in the peptide chain by this process. A structure-activity correlation in the series of cyclosporine derivatives thus available is discussed.

Synthesis of Pyridine and Dihydropyridine Derivatives by Regio- and Stereoselective Addition to N-Activated Pyridines

Abstract: Stereoselective Addition to N-Activated Pyridines James A. Bull,‡ James J. Mousseau, Guillaume Pelletier,† and Andre ́ B. Charette*,† †Department of Chemistry, Universite ́ de Montreál, P.O. Box 6128, Station Downtown, Montreál, Queb́ec, Canada H3C 3J7 ‡Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, U.K. Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA