Method for transfer of labeled methyl groups

Abstract

1697crystals which had formed were separated by fitration and washed with a little cold cyanomethane. Chromatography on a 1 in. X 18 in. CC-7 silica gel column (CH2C12) gave yellow needles from the yellow-orange band. Recrystallization from cyanomethanewater afforded 420 mg (68%) of 10: mp 173-174 "C; NMR (CDClJ 6 7.67 (m,5, CsH5), 8.72 (d, 1, 8.80 (d, 1, H-4); UV max (ether) 268 nm (t 38600), 295 (43400), 322 (sh, 9650), 422 (3380); mass spectrum, m / z 383.8676 (M' calcd for C1&7N279Br23SC1: 383.8666), with the natural abundances of %r, 81Br, %C1, and 37Cl. 7-Bromo-and 5,7-Dibromo-2H-cyclopenta[ dlpyridazine (11). To a stirred solution of 230 mg (1.95 mmol) of 2H-cyclopenta[d]pyridazine8 in 60 mL of cyanomethane cooled by a dry ice bath was added a solution of 357 mg (2.01 mmol) of NBS7 in ca. 15 mL of cyanomethane over a period of 1 h. TLC (9:l CH2C12-ether) showed three components, one corresponding to starting material. NMFt indicated a 253 ratio for starting material and the two products, respectively. Additional NBS solution was added slowly with periodic TLC monitoring until no starting material was present [ca. 200 mg (1.12 "01) of NBS]. A mixture of the products was isolatd by solvent removal (rotary evaporator) and chromatography 011 a 1 in. X 2 in. CC-7 silica gel column (CH2C1J. The separation of the products was accomplished with difficulty on an analytical TLC plate with %lo CH2C12-acetone. The 7-bromo compound was removed with ether and amounted to 29.

p-Methoxybenzyl Ether Cleavage by Polymer-Supported Sulfonamides

“…p-toluenesulfonamide (5) 6 (Figure 2). Complete removal of the PMB group was observed, and sulfonamide 3 and menthol (6) were generated.…”

“…p-toluenesulfonamide (5) 6 (Figure 2). Complete removal of the PMB group was observed, and sulfonamide 3 and menthol (6) were generated. Importantly, PMB removal was not observed when sulfonamide 5 was omitted from the reaction.…”

“…To determine if the process is general, compound 4 was treated with 0.1 equiv of TfOH in the presence of N -methyl- p -toluenesulfonamide ( 5 ) (Figure ). Complete removal of the PMB group was observed, and sulfonamide 3 and menthol ( 6 ) were generated.…”

Continuous Production of the Diazomethane Precursor N-Methyl-N-nitroso-p-toluenesulfonamide: Batch Optimization and Transfer into a Microreactor Setup

“…In the literature, various reports describe the discontinuous synthesis of 2 − with yields >70% on laboratory scale. Due to the exothermal behavior of the reaction, cooling is applied and the amine added slowly.…”

The Shortest Route to Chiral Ditosylmethylamine

“…Among the most powerful syntheses of the smallest asymmetric molecule,3–5 the most attractive deal with the preparation of chiral N , N ‐ditosylmethylamine. This synthon is of particular interest since it can be considered to be a bridgehead in obtaining numerous substrates that bear an enantiomerically enriched methyl group by means of a facile S N 2 reaction 6. Although very elegant, Floss's approach, in which chiral acetic acid is converted into the corresponding methylamine by means of a Schmidt degradation, suffers from problems of reproducibility, sometimes resulting in the marked loss of enantiomeric purity of the starting enantiomerically enriched acetic acid 7.…”