P-Toluenesulfonic acid, hydrate

These observations can be extrapolated to the pyrrole series the 2-amino derivatives are very unstable whereas 3-aminopyrroles appear to be more stable. 3-Amino-l-tritylpyr-role (162) appears to exist in solution exclusively in the imino-A -pyrroline form (163) (83JCS(P1)93). 2-Aminoindole (164) is unusual in that it exists mainly as the 3//-tautomer (165). 4-Alkylaminoindoles (166) undergo an unexpected rearrangement to 4-amino-1-alkylindoles (167) when heated with p-toluenesulfonic acid hydrate (82CC1356). 

To a 125-mL Erlenmeyer flask containing a stirring bar is added 1.078 g (2.000 mmol) of tricarbonyl(hydrido)[l,2-bis(diphenylphosphino)ethane] manganese in 60 mL of methylene chloride. To the stirred solution, 2.11 g (11.1 mmol) of solid p-toluenesulfonic acid hydrate is added in small increments. The theoretical quantity of dihydrogen is evolved in less than 10 min. The suspension is washed twice with equal volumes of water, then with dilute sodium bicarbonate solution, then with water again. The methylene chloride is evaporated to dryness and the product is crystallized from benzene methylene chloride (2 1) to give yellow crystals in 77% yield. 

Alkylaminoindoles (302) rearrange to 4-amino-l-alkylindoles (303) when heated with p-toluenesulfonic acid hydrate (82CC1356). 

This benziodazole reacts not only with Me3SiN3, as already mentioned, but also with p-toluenesulfonic acid hydrate or methanesulfonic acid in acetic anhy-... 

The Step 2 product (0.40 mmol) suspended in methyl alcohol/water, 10 1, was treated with p-toluenesulfonic acid hydrate (0.04 mmol), then stirred 18 hours at ambient temperature, and then diluted with EtOAc. The organic solution was washed twice with saturated NaHC03 solution, once with brine, dried using Na2S04, filtered, and concentrated. The residue was recrystallized from EtOAc and heptane and the solid washed with heptane/CH2Cl2, 1 1. The solid was dried in vacuo at 60 C and the product isolated in 70% yield as a white solid. The product shrinks at 90.8°C, mp= 115-117°C. 

The yield of dimethylphosphine can be increased by increasing the amount of tributylphosphine which allows use of water in the less volatile form of a hydrate. Thus using the same apparatus, procedure and with the same amount of tetramethyldiphosphine disulfide, using 50.5 g (250mmole) P(n-C4H9)3 and 15.2 g (80mmole) p-toluenesulfonic acid hydrate, the yield of dimethylphosphine is 7.1 g (95%). 

A suspension of benzyl 2-acetoxymethyl-3-(2-methoxycarbonylethyl)-4-methyl-pyrrole-5-carboxylate and 3-acetyl-2,4-dimethylpyrrole in methanol treated with p-toluenesulfonic acid hydrate, and warmed 4 hrs. at 35 under Ng -> product. Y 91%. F. e., also tripyrranes, s. A. M. d A. Rodia Gonsalves, G. W. Kenner, and K. M. Smith, Tetrah. Let. 1972, 2203. 

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