ChemInform Abstract: UMPOLUNG (DIPOLE INVERSION) OF CARBONYL REACTIVITY

Abstract

In einer Übersicht mit 68 Literaturhinweisen wird die "Umpolung" der Carbonylreaktivität (Umkehr der normalen Reaktivität) behandelt.

Lithium aluminum hydride-aluminum hydride reduction of sultones

“…Slow addition of 209 mL of 2.2 M n-butyllithium to a solution of 113.6 g (0.42 mol) of the dimesylate of trans-1,2cyclohexanediol in 1.8 L of THF under nitrogen at -78 °C was followed by stirring at -78 °C for 1 h. The mixture was allowed to warm to room temperature and to stand for 42 h. The usual workup gave a crude yellow oü which solidified on being allowed to stand and proved to be largely the starting dimesylate of trans-1,2-cyclohexanediol. The crude product was chromatographed on an alumina column by elution with methylene chloride followed by ether to give, after recrystallization from pentane-ether, 1.4 g (1.9%) of the trans sultone 20 as white needles: mp 9),2), ppm (dt, 1); mass spectrum, m/e (relative intensity) 176 (2), 112 (47), 95 (20), 94 (91), 84 (44), 83 (48), 81 (26), 79 (74), 71 (28), 70 (65), 69 (42), 68 (100), 67 (33), 66 (20), 57 (60), 56 (55), 55 (73), 54 (49), 53 (41).…”

“…The competition is largely determined by the steric environment of the -carbon. This is seen in the case of sultones [1][2][3][4][5] where the -carbon is primary and where aluminum hydride leads to complete destruction of the sultone and the failure to recover organic products by employing the usual workup procedure. In the case of propane sultone 1, a modified and tedious isolation procedure followed by derivatization led to propanesulfonamide ( 44), demonstrating the validity of the assumption of hydride displacement at the -carbon and C-0 bond cleavage (eq 4).…”

The Strength of Weak Interactions: Aromatic Fluorine in Drug Design

“…A second consequence of aromatic fluorination is Umpolung [21] of the typical benzene quadrupole. The intramolecular charge redistribution resulting from fluorine substitution on benzene is shown in Fig.…”

Preparation of 3-acetamido-2,5-dihydrothiophenes

“…Caled for Ct3Hi3NO;tS: C, 59.30; H, 4.98; N. 5.32. Found: C, 59.01; H, 4.83; N, 5.22. l-Thiaspiro[4.5]decane-4,6-dione (9). A mixture of 40 g (0.2 mol) of 2-(carboxyethvlthio)cyclohexanone,12 250 mL of benzene, 25 mL of triethylamine, and 50 mL of acetic anhydride was heated under reflux for 1 h, allowed to stand at room temperature overnight, stirred for 3 h with 25 mL of water, and diluted with 250 mL of ether.…”