Bromophloroglucinols and their methyl ethers

Abstract

All 16 bromination products of phloroglucinol and its methyl ethers, as well as five bromoresorcinols and three of their dimethyl ethers, were synthesized and analyzed by nuclear magnetic resonance spectroscopy. Two or three equivalents of bromine convert phloroglucinol to di-and tribromophloroglucinol, 5-methoxyresorcinol to the tri-and 2,4-dibromo, 3,s-dimethoxyphenol to the tri-and 2,6-dibromo, and 1,3,5-trimethoxybenzene to the dibromo compound. With one equivalent of bromine, 3,s-dimethoxyphenol reacts preferentially at C-2 while 5-methoxyresorcinol gives both monobromo isomers. Partial debromination with sodium sulfite yields successively 2,4-dibromo-and 2-bromo-5-methoxyresorcinol from the tribromo compound but fails with brominated 3,s-dimethoxyphenol. In the resorcinol series, C-2 is invariably the least reactive position.4,6-Dibromo-5-methoxyresorcinol and 2,4-dibromo-3,s-dimethoxyphenol are accessible by methylation of dibromophloroglucinol, obtained from 3,s-dibromo-2,4,6-trihydroxybenzoic acid by decarboxylation. In contrast to resorcinol and tribromoresorcinol, the partial bromination of phloroglucinol and debromination of tribromophloroglucinol are not selective. The 13cmr spectra of bromophloroglucinol methyl ethers show characteristic downfield shifts for methoxy groups orthogonal to the aromatic ring plane.Key words: bromophloroglucinols, synthesis, nmr, and debromination; bromo-5-methoxyresorcinols, synthesis, nmr, and debromination; bromo-3,s-dimethoxyphenols, synthesis and nmr. On a effectuC la synthtse des 16 produits de bromination du phloroglucinol et de ses Cthers mCthyliques ainsi que de cinq bromorCsorcinols et de trois de leurs Cthers dimCthyliques et on a pu effectuer une analyse de tous ces dCrivCs par spectroscopie en rksonance magnttique nuclCaire. Deux ou trois Cquivalents de brome transforment le phloroglucinol en di-et en tri-bromophloroglucinols, le mCthoxy-5 rtsorcinol en dCrivCs tribromo et dibromo-2,4, le dimCthoxy-3,s phCnol en dCrivCs tribromo et dibromo-2,6 et le trimCthoxy-1,3,5 benzkne en composC dibromC. Avec un Cquivalent de brome, le dimtthoxy-3,s phtnol rCagit prCf6rentiellement en C-2 alors que le mCthoxy-5 rCsorcinol foumit les deux isomkres monobromCs. Si on soumet le dCrivC tribromC i une dCbromation partielle i I'aide de sulfite de sodium, on obtient successivement le dibromo-2,4 et le bromo-2 mCthoxy-5 rCsorcinol; toutefois, on ne peut effectuer de dkbromation partielle sur le dimCthoxy-3,s phCnol bromC. Dans la sCrie du rCsorcinol, la position C-2 est toujours la moins reactive. Les dibromo-4.6 mCthoxy-5 rCsorcinol et dibromo-2,4 dimCthoxy-3,s phCnol sont accessibles par mCthylation du dibromophloroglucinoI qui est obtenu par dCcarboxylation de l'acide dibromo-3,s trihydroxy-2,4,6 benzoi'que. Par opposition avec ce qui est observC avec le rCsorcinol et le tribromorCsorcinol, la bromation partielle du phloroglucinol et la dCbromation du tribromophloroglucinol ne sont pas sClectives. Dans les spectres rmn du I3c des Cthers mCthyliques des bromophloroglucinols,...

Polyols as Templates for the Synthesis of Macrocycles from Boronic Acid Building Blocks

“…[24] Starting from 2-bromoresorcinol (3), [25] the phenol groups were alkenylated, first giving the bromide 4 in 94 % yield. Lithiation, reaction with trimethyl borate and hydrolysis yielded the desired boronic acid 5 in 77 % yield.…”

“…2-Bromo-1,3-dihydroxybenzene [25] was prepared according to literature procedures. Dry solvents were obtained with suitable desiccants.…”

Tetraols as Templates for the Synthesis of Large endo‐Functionalized Macrocycles

“…Remarks: The following chemicals were obtained commercially and were used without further purification: Acetic anhydride (Acros), amberlite IR-120 (H + form, Merck), (benzylidene)(dichloro)-bis(tricyclohexylphosphane)ruthenium (Aldrich), borane-tetrahydrofuran complex (Alfa Aesar), 7-bromoheptene (Aldrich), 11 [10] 2,6-bis(pent-4-enyloxy)phenylboronic acid (1a), [16] 2,6-bis(hex-5-enyloxy)phenylboronic acid (1b), [15] 2,6-bis(oct-7-enyloxy)phenylboronic acid (1d), [10] and 2-bromo-1,3-dihydroxybenzene [17] were prepared according to literature procedures. Dry solvents were obtained with suitable desiccants.…”

Towards Allosteric Receptors – Synthesis of Resorcinarene‐Functionalized 2,2′‐Bipyridines and Their Metal Complexes

“…Phenylboronic acid 27 was synthesized starting from resorcinol which was first halogenated with iodine or bromine following literature procedures to yield 2-iodo- [20] and 2-bromoresorcinol [21,22] (28) and (30) in one and in two steps, respectively, in about 70 % (Scheme 15).…”

“…Was synthesized from 1,3,5-tribromo-2,4-dihydroxybenzene (19.3 g, 55.5 mmol) using sodium sulfite (13.8 g, 111 mmol) and sodium hydroxide (4.33 g, 111 mmol) in water (139 mL) and methanol (28 mL) following a literature procedure [21] to yield 9.00 g (47.6 mmol, 86 %) of colourless needles, ref.…”