An effective method for the protection of carboxylic acids with a triisopropylsiloxymethyl (TIPSOCH2) group is described. The reactions of various carboxylic acids with C12H25SCH2OTIPS in the presence of CuBr2, Et3N, and molecular sieves 4A afford the corresponding triisopropylsiloxymethyl esters in good yields.
To provide a method for performing a cross-coupling reaction of a Grignard compound with an alkyl halide simply, efficiently and in high yield, a method for obtaining a ω-bromo long chaincarboxylic acid simply and efficiently using an easily obtainable raw material and a method for producing a useful branched fatty acid simply and efficiently.
[R
1
: an alkyl group having 1 to 15 carbon atoms, R
2
: an alkyl group having 1 to 30 carbon atoms with a carboxyl group and X and X′: a halogen atom]
[n: an integer of 9 to 17]
[n: an integer of 9 to 17, R
1a
: a branched alkyl group having 3 to 8 carbon atoms and X: a halogen atom]
We show reproducible, stable negative differential resistance (NDR) at room temperature in molecule-controlled, solvent-free devices, based on reversible changes in molecule-electrode interface properties. The active component is the cyclic disulfide end of a series of molecules adsorbed onto mercury. As this active component is reduced, the Hg-molecule contact is broken, and an insulating barrier at the molecule-electrode interface is formed. Therefore, the alignment of the molecular energy levels, relative to the Fermi levels of the electrodes, is changed. This effect results in a decrease in the current with voltage increase as the reduction process progresses, leading to the so-called NDR behavior. The effect is reproducible and repeatable over more than 50 scans without any reduction in the current. The stability of the system, which is in the "solid state" except for the Hg, is due to the molecular design where long alkyl chains keep the molecules aligned with respect to the Hg electrode, even when they are not bound to it any longer.
SATO TOSHIO; KAWARA TATSUO; KOKUBU YASUCHIKA; FUJISAWA TAMOTSU, BULL. CHEM. SOC. JAP., 1981, 54, NO 3, 945-946