Phosphine → 2-Diazofluorene

HRID 540998

Reaction equation

HRID 540998 reaction equation
[N:1]([CH:4]1[C:16]2[CH:15]=[CH:14][CH:13]=[CH:12][C:11]=2[C:10]2[C:5]1=[CH:6][CH:7]=[CH:8][CH:9]=2)=[N+:2]=[N-].P>C1(C)C=CC=CC=1>[N+:1](=[C:4]1[C:16]2[CH:15]=[CH:14][CH:13]=[CH:12][C:11]=2[C:10]2[C:5]1=[CH:6][CH:7]=[CH:8][CH:9]=2)=[N-:2]

Participants

4

Reactant 2

HCID 24404PhosphineHCID 43300859-azido-9H-fluorene

Product 1

HCID 700282-DiazofluoreneYield 85%

Reagents, catalysts & solvents 1

HCID 1140TolueneSolvent

Procedure

To probe the scope of the reaction even further, we investigated the synthesis of semi-stabilized diazo-compounds. Treatment of 9-azido-fluorene 2j with phosphine 1e under anhydrous conditions at low temperature (toluene, 0° C.), followed by loading the red solution directly on basic alumina (Grade 5) and eluting with 10% CH2Cl2/hexanes, 9-diazo-fluorene 5j was isolated in 85% yield and excellent purity (96%). Apparently, thermal fragmentation of the putative triazenophosphonium salt, which more than likely exists in its neutral λ5-phosphorane form[16] is suppressed sufficiently for this substrate under the reaction conditions. The low temperature and low polarity of the solvent probably contribute to that greater stability. Under the standard conditions (THF/H2O), incomplete conversion of the azide 2j and contamination of the diazo-compound 5j with substantial amounts of other products, probably arising from alternative triazene decomposition and dimerization of the diazo-compound, were apparent. Finally, a vinylogous diazo-carbonyl compound 5k (96% purity) was prepared in good yield from anthraquinone-based azide 2k using the standard conditions.

Workup

  1. customthe scope of the reaction even further
  2. customthe synthesis of semi-stabilized diazo-compounds
  3. washeluting with 10% CH2Cl2/hexanes

Sources & evidence

ORD record
ord-600bdc5568d2458d8fe568d04ab3f2d8
Source dataset
uspto-grants-2014_10
Patent number
US08871916B2

Linked notes

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