Reaction with phloroglucinol

In terms of the average fi om 20 mature fiiiits, floss silk, seeds and fruit coat were isolated, the ratio being 14 %, 15 % and 71 % respectively. The filaments of floss silk on submission to microscopy, showed mainly unicellular trichomas, some of them being formed by two cells. The presence of lignin in the filaments was suggested by the characteristic reaction with phloroglucinol hydrochloride. 

Fungi. I. Metabolic Products otLentinus lepideus. Biochem. J. 34. 82 (1940). 7a. Black, R. A., A. A. Rosen and S. L. Adams The Chromatographic Separation of Hardwood Extractive Components Giving Color Reactions with Phloroglucinol. J. Amer. chem. Soc. 75, 5344 (1953). 

Color Reaction with Phloroglucinol-Hydrochloric Acid... 

Lignin gives characteristic colour reactions. With phloroglucinol and hydrochloric acid it turns red, with aniline sulphate, yellow. 

Black R A, Rosen A A, Adams S L 1953 The chromatographic separation of hardwood extractive components giving color reactions with phloroglucinol. J Am Chem Soc 75 5344-5346... 

Furfural gives two characteristic colour reactions which serve for qualitative detection. With phloroglucinol and hydrochloric acid (1 part concentrated acid, 1 part water) a cherry-red colour is produced on boiling with a solution of aniline acetate a red colour is produced even in the cold. 

The reaction of the dimethyl acetal of phenylacetaldehyde with salicylaldehydes enables 3-phenylbenzopyrylium salts to be prepared (82JHC97) and the reaction of arylmalondial-dehydes with phloroglucinol provides another variation on this theme which also affords isoflavylium salts (81AJC2647). 

Based on this tautometism, certain addition and replacement reactions at the hydroxyl or keto groups can be effected easily as with certain reactions of resorcinol and 2-naphthalenol. Thus, phloroglucinol forms a trioxime with hydroxylamine (120) it forms mono-, di-, and ttiaddition compounds with sodium bisulfite (121) it undergoes the Bucherer reaction with ammonia at room temperature (122) to give at first phloramine... 

Trinitrosophloroglucinol is obtained by reaction of phloroglucinol with nitrous acid in acetic acid (135). 

Protonated phenols and phenol ethers formed in superacids can be trapped by aromatics (benzene, naphthalene, tetrahydroquinoline). The products are either cyclohexenone derivatives301 [Eq. (5.112)] or aryl-substituted phenols. In the reaction of phloroglucinol with benzene, the diphenyl-substituted derivative is the main product [Eq. (5.113)], whereas 1,3,5-trimethoxybenzene gives selectively the monophenyl derivative (80% yield). Protonated dicationic species, such as 76, detected by Olah and Mo302 using NMR, were suggested to be intermediates in these processes. 

Figure 4-6. Reaction of phloroglucinol with coniferaldehyde end-groups in the lignin under acidic conditions results in the formation of a red chromophore.

An amorphous preparation was made similarly from 2,3,4,6-tetra-O-acetyl-(2-hydroxy-D-galactal).9 It was noted that this preparation did not give the reactions reported by Helferich for the 5,6-anhydro derivative with pyrogallol, orcinol, aniline, and m-nitroaniline. However, it did give a voluminous, red-brown precipitate with phloroglucinol. 

Phenols react with cinnamyl compounds via an intermolecular condensation/cyclization providing a reliable method for the construction of dihydrocoumarins. Montmorillonite K-10 clay can catalyze the condensation/cyclization reaction of phloroglucinol and cinnamoyl chlorides to provide a high-yielding route to dihydrocoumarins (Equation 416) <2001S2247>. 

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