Bulky Isopropyl Group Research Articles

Studies on the Alkylation of 5′-CMP under Alkaline Conditions

The reaction of 5′-CMP with methyl, ethyl, n-propyl and isopropyl iodides gave predominantly ribose alkylated products. Various alkylated derivatives have been characterized using UV spectroscopy, paper electrophoresis, 1H NMR and FAB (negative) mass spectroscopic techniques. Under strongly alkaline conditions the 2′-O-alkylated derivatives are synthesized in maximal yields. Isopropylation reaction gave only a small yield of the 3′-O-isopropyl derivative, this could be explained on the basis of steric hindrance offered to the bulky isopropyl group at the 2′-OH position by the heterocyclic base of the nucleotide.

Conformations of 2-substituted 2,3-dihydro-1,4-benzodioxines

X-Ray crystallographic studies have shown that the imidazolinium group in 2-(2-methoxy-2,3-dihydro-1,4-benzodioxin-2-yl)-4,5-dihydroimidazolium bromide (4), (+)-2-(2-methoxy-2,3-dihydro-1,4-benzodioxin-2-yl)-4,5-dihydroimidazolium hydrogen dibenzoyltartrate (5), and 2-(2,3-dihydro-1-benzopyran-2-yl)-4,5-dihydroimidazolium chloride (7) occupies the equatorial position on the dihydroxine ring of compounds (4) and (5) and the dihydropyran ring of compound (7). The imidazolium group in 2-(2,3-dihydro-1,4-benzodioxin-2-yl)-4,5-dihydroimidazolium chloride (2), (+)-2-(2,3-dihydro-1,4-benzodioxin-2-yl)-4,5-dihydroimidazolium hydrogen dibenzoyltartrate (3), and 2-(2-isopropyl-2,3-dihydro-1,4-benzodioxin-2-yl)-4,5-dihydroimidazolium chloride (6) occupies the axial position on the dihydrodioxine ring; the axial choice in compound (6) is attributed to the equatorial preference of the bulky isopropyl group, and the conformational anomaly in compounds (2) and (3) appears to be caused by an interaction between the axial imidazolium group and a lone-pair orbital on the oxygen atom O(4) of the dihydrodioxine ring.

SYNTHESIS AND REDOX BEHAVIOR OF [Mo(2,4,6-TRIALKYLBENZENETHIOLATO)4]. UNIQUE REDOX PROPERTIES OF TETRA-COORDINATED Mo(IV) COMPLEXES WITH BULKY THIOLATES

Abstract Two new molybdenum(IV) complexes having bulky thiolato ligands, [Mo(2,4,6-trimethylbenzenethiolato)4] and [Mo(2,4,6-triisopropylbenzenethiolato)4], were synthesized. These complexes show paramagnetic properties due to a nearly tetrahedral coordination and exhibit the quasi-reversible redox couples of Mo(V)/Mo(IV) at −0.07 V and +0.47 V vs. SCE, respectively in 1,2-dimethoxyethane. The two bulky isopropyl groups at o-position prevent π-interaction between Mo(IV) and sulfur, providing an ionic character at the Mo–S bond and stabilizing Mo(IV) state against oxidation.

Thermal rearrangement of divinylcyclopropane systems. Preparation of functionalized, stereochemically defined bicyclic and tricyclic products containing the bicyclo[3.2.1]octane skeleton

A study involving the preparation and thermolysis of substituted 6-exo-(1-alkenyl)bicyclo[3.1.0]hex-2-ene systems (14, 15, 23, 29, 40) shows (a) that C-8 functionalized bicyclo[3.2.1]octa-2,6-dienes can be prepared readily via this methodology (14 → 16; 15 → 17), (b) that the rearrangement reaction is stereospecific even when the 6-(1-alkenyl) group is substituted with a sterically bulky isopropyl group (23 → 24; 29 → 30), and (c) that the method can be extended to include the preparation of tricyclic systems (40 → 41).

Bis-(diisopropoxyphosphinyl)-methane complexes with rare-earth nitrates and chlorides

Solid adducts of rare-earth nitrates or chlorides and bis-(diisopropoxyphosphinyl)-methane were prepared and characterized by chemical and spectroscopic methods. A structural change observed for the nitrate adducts in traversing the lanthanide series is considered to be a shift from monomeric to dimeric form, caused by increasing steric repulsion between the bulky isopropyl groups as the metal ion becomes smaller. It is postulated that the ratio of unidentate to bidentate bonding of the nitrate groups also varies.