Trifluoroacetic acid → benzyl 1-ethyl-1H-spiro[chromeno[4,3-c]pyrazole-4,4'-piperidine]-1'-carboxylate

HRID 1908027Notes

Reaction equation

HRID 1908027 reaction equation
[CH2:1]([N:3](C(OC(C)(C)C)=O)[NH2:4])[CH3:2].O[CH:13]=[C:14]1[C:23]2([CH2:28][CH2:27][N:26]([C:29]([O:31][CH2:32][C:33]3[CH:38]=[CH:37][CH:36]=[CH:35][CH:34]=3)=[O:30])[CH2:25][CH2:24]2)[O:22][C:21]2[C:16](=[CH:17][CH:18]=[CH:19][CH:20]=2)[C:15]1=O.C(O)(C(F)(F)F)=O.NN>ClC(Cl)C.ClCCl.C(=O)(O)[O-].[Na+]>[CH2:1]([N:3]1[C:15]2[C:16]3[CH:17]=[CH:18][CH:19]=[CH:20][C:21]=3[O:22][C:23]3([CH2:28][CH2:27][N:26]([C:29]([O:31][CH2:32][C:33]4[CH:38]=[CH:37][CH:36]=[CH:35][CH:34]=4)=[O:30])[CH2:25][CH2:24]3)[C:14]=2[CH:13]=[N:4]1)[CH3:2]

Participants

8

Reactant 4

HCID 6422Trifluoroacetic acid2×HCID 9321HydrazineHCID 57517432N-ethyl(tert-butoxy)carbohydrazideHCID 67463745Benzyl 3-(hydroxymethylene)-4-oxo-spiro[chromane-2,4'-piperidine]-1'-carboxylate

Product 1

HCID 58551072benzyl 1-ethyl-1H-spiro[chromeno[4,3-c]pyrazole-4,4'-piperidine]-1'-carboxylateYield 65.7%

Reagents, catalysts & solvents 3

HCID 6344DichloromethaneSolventHCID 63651,1-DichloroethaneSolventHCID 516892Sodium BicarbonateSolvent

Procedure

A mixture of tert-butyl 1-ethylhydrazinecarboxylate (320 mg, 2.0 mmol) and benzyl 3-(hydroxymethylene)-4-oxo-spiro[chromane-2,4′-piperidine]-1′-carboxylate (770 mg, 2.0 mmol) in dichloroethane (5 mL) was allowed to stir at 25° C. with TFA (78 μL, 1.0 mmol) for 2 h. Once LC/MS analysis showed complete imine formation, more TFA was added to deprotect the hydrazine and cyclize the product. The reaction was diluted with dichloromethane, and aqueous sodium bicarbonate was added with stirring. The layers were separated and the organics were further washed with saturated aqueous sodium bicarbonate and brine. The organics were dried over sodium sulfate and evaporated to dryness. The crude material was purified by column chromatography (0-100% ethyl acetate in hexanes) to afford benzyl 1-ethyl-1H-spiro[chromeno[4,3-c]pyrazole-4,4′-piperidine]-1′-carboxylate (530 mg, 65%). ESI-MS m/z calc. 403.2. found 404.7 (M+1)+; Retention time: 1.94 minutes (3 min run). 1H NMR (400 MHz, CDCl3) δ 7.49 (d, J=7.6 Hz, 1H), 7.40-7.29 (m, 4H), 7.29-7.19 (m, 2H), 7.10-6.99 (m, 2H), 5.16 (s, 2H), 4.47 (q, J=7.3 Hz, 2H), 4.15-3.95 (m, 2H), 3.45-3.26 (m, 2H), 2.15-2.03 (m, 2H), 1.88-1.78 (m 2H), 1.54 (t, J=7.3 Hz, 4H).

Workup

  1. additionwas added
  2. additionwas added
  3. customThe layers were separated
  4. washthe organics were further washed with saturated aqueous sodium bicarbonate and brine
  5. dry with materialThe organics were dried over sodium sulfate
  6. customevaporated to dryness
  7. customThe crude material was purified by column chromatography (0-100% ethyl acetate in hexanes)

Sources & evidence

ORD record
ord-1aa2059fa17941fd810df3ee39269875
Source dataset
uspto-grants-2013_12
Patent number
US08598164B2

Reaction notes

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