Selective Demethylation of Aryl Methyl Ethers

The first synthesis of [2‐13C]phloroglucinol

“…Cyclization to [2][3][4][5][6][7][8][9][10][11][12][13] C]cyclohexane-1,3-dione 7 was successful in dry tetrahydrofuran, using carefully dried potassium tert-butoxide 7 The desired product 8 was isolated in a 70% yield after purification.…”

“…Purification by column chromatography gave the desired 3,5-dimethoxy- [4-13 C]phenol 10 in 59% yield. Finally, demethylation was required to complete the synthesis of [2][3][4][5][6][7][8][9][10][11][12][13] C]phloroglucinol 1b. A range of conditions was examined, and it was found that treatment of 10 with boron tribromide solution (10 equivalents) in dichloromethane (À781C to rt) gave the cleanest results and highest yields.…”

“…A range of conditions was examined, and it was found that treatment of 10 with boron tribromide solution (10 equivalents) in dichloromethane (À781C to rt) gave the cleanest results and highest yields. 9 After purification by column chromatography, [2][3][4][5][6][7][8][9][10][11][12][13] C]phloroglucinol 1b was obtained in 81% yield (9% overall yield from 5 over th 6 steps). The 13 C-atom was clearly observed as an enhanced singlet at 93.9 ppm in the 13 C NMR spectrum.…”

“…A new synthetic route to [2-13 C]phloroglucinol 1b has been developed, which uses a modification of the iridium catalysed C-H activation/borylation/oxidation procedure recently published by Maleczka et al 6 Using this methodology, a hydroxyl group can be inserted into the 3-position of [2-13 C]resorcinol 2a to give [2-13 C]phloroglucinol 1b, the first single 13 C-labelled derivative of phloroglucinol to be reported.…”

Absolute configuration of (+)-?-dihydrotetrabenazine, an active metabolite of tetrabenazine

“…), and Department of Energy Grant DOE-DE-FG021-87ER60651. (4) 636 (4) 3051 (3) 9857 (4) 48 (1) C (5) 1709 (4) 2723 (3) 9052 (3) 42 (1) C (6) 1468 (4) 1886 (3) 8226 (3) 43 (1) C (7) 2618 (5) 1490 (4) 7365 (4) 55 (1) C (8) 4067 (5) 1854 (3) 7817 (5) 54 (1) N (1) 4008 (3) 3003 (2) 7992 (3) 40 (1) C (9) 3112 (4) 3298 (3) 9139 (4) 45 (1) C (10) 2971 (4) 4461 (3) 9133 (4) 50 (1) C (11) 4398 (4) 5007 (3) 9241 (4) 45 (1) O (3) 4213 (3) 6097 (2) 9252 (3) 52 (1) C (12) 5363 (4) 4658 (3) 8151 (4) 46 (1) C (13) 5417 (5) 3477 (3) 8145 (6) 50 (1) C (14) 6837 (5) 5140 (4) 8309 (6) 62 (1) C (15) 7918 (5) 4861 (4)…”