Reaction #631984

Reaction equation

N′-(5-ethyl-2,3-dihydro-benzo[1,4]dioxine-6-carbonyl)-hydrazinecarboxylic acid tert-butyl ester

trifluoroacetic acid

NaOH H2O

→

5-ethyl-2,3-dihydro-benzo[1,4]dioxine-6-carboxylic acid hydrazide

Yield 129.9%

Solvents

water

Conditions

Workup

1. 1
   workup.STIRRINGwith stirring, until the acid
2. 2
   OtherThe reaction mixture was transferred to a separatory funnel
3. 3
   Extractionextracted with ethyl acetate
4. 4
   workup.STIRRINGby shaking gently (caution: gas evolution)
5. 5
   ExtractionThe ethyl acetate extract
6. 6
   Otherwas dried
7. 7
   Otherevaporated
8. 8
   Otherto yield 5.51 g of a pale, viscous yellow semi-solid
9. 9
   Otherwas then placed in a 50° C.
10. 10
    Otherfor about 1 hour

Procedure

5.15 g (16 mmol) of N′-(5-ethyl-2,3-dihydro-benzo[1,4]dioxine-6-carbonyl)-hydrazinecarboxylic acid tert-butyl ester were added to a 200 mL round bottom flask. About 20 mL of trifluoroacetic acid were added and the reaction mixture was stirred at room temperature for 24 hours. Then about 40 mL of water were added, followed by the slow addition of cold 10% NaOH/H2O, with stirring, until the acid was neutralized (pH˜14). The reaction mixture was transferred to a separatory funnel and extracted with ethyl acetate by shaking gently (caution: gas evolution). The ethyl acetate extract was dried and evaporated to yield 5.51 g of a pale, viscous yellow semi-solid. The material was then placed in a 50° C. vacuum oven for about 1 hour to yield 4.62 g of 5-ethyl-2,3-dihydro-benzo[1,4]dioxine-6-carboxylic acid hydrazide. The t-Boc cleavage is best accomplished with neat trifluoroacetic acid; use of adjunctive solvents always resulted in much lower yields. 1H NMR (CDCl3, 500 MHz) δ (ppm): 7.0 (br, 1H), 6.83 (m, 1H), 6.71 (m, 1H), 4.28 (br s, 4H), 2.76 (m, 2H), 1.6 (br, 2H), 1.17 (t, 3H).

Source