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Buchwald-Hartwig coupling of benzophenone imine with 4,7-dibromobenzo[c]-1,2,5-thiadiazole ; N,N'-(benzo[c]-1,2,5-thiadiazole-4,7-diyl)bis(1,1-diphenylmethanimine)

SyntheticPage 909
DOI: 10.1039/SP909
Submitted Aug 26, 2019, published Sep 05, 2019
Kathryn Allen (kathryn.allen@millersville.edu), Steven Knauss (sjknaus1@millersville.edu)
A contribution from Allen Group @ MU of PA


			Reaction Scheme: Buchwald-Hartwig coupling of benzophenone imine with 4,7-dibromobenzo[<em>c</em>]-1,2,5-thiadiazole&nbsp;

Chemicals Used

Anhydrous toluene, 99.8%, Aldrich
4,7-Dibromobenzo[c]-1,2,5-thiadiazole, 95%, Aldrich
1,1′-Ferrocenediyl-bis(diphenylphosphine) (DPPF), 97%, Aldrich
Palladium (II) acetate, reagent grade, 98%, Aldrich
Sodium tert-butoxide, 97%, Aldrich
Benzophenone imine, 95%, Aldrich

Procedure

An oven-dried three-necked round bottom flask and stir bar was equipped with three septa and purged with dry nitrogen gas for 30 minutes. Anhydrous toluene (5.6 mL, 0.18 M), 4,7-dibromobenzo[c]-1,2,5-thiadiazole (293.9 mg, 1.00 mmol, 1 eq.), DPPF (27.7 mg, 0.05 mmol), palladium (II) acetate (16.8 mg, 0.075 mmol), and sodium tert-butoxide (211.4 mg, 2.20 mmol, 2.2 eq.) were added to the flask. Benzophenone imine (0.34 mL, 2.00 mmol, 2 eq.) was added dropwise by syringe under nitrogen. The solution was heated to 90°C for 24 hours. On workup, the solution was diluted with water, and washed with ethyl acetate. The water layer was washed with dichloromethane. The organic layers were combined, dried over magnesium sulfate and filtered. The solvent was removed under reduced pressure to yield a thick, dark red oil. The oil was taken up in hot hexanes and cooled to room temperature and filtered to yield a brick-red powder (326.8 mg, 0.66 mmol, 66% yield).

Author's Comments

Recrystallization of the thick, dark red oil was futile due to solubility problems -- the oil does not dissolve. However, heating the oil in hexanes to yield a heterogeneous mixture, then cooling the mixture yielded a perfectly clean dark red solid that could be readily separated from the filtrate to yield pure product.  Before hexanes, the crude product was very impure with unidentified side product. 

Data

1H NMR (400 MHz, CDCl3) δ 7.820 (d, J = 8 Hz, 4H), 7.491 (m, 2H), 7.411 (m, 4H), 7.209 (m, 2H), 7.129 (m, 4H), 7.057 (d, J = 8 Hz, 4H), 6.456 (s, 2H).

13C NMR (400 MHz, CDCl3) δ 171.090, 149.635, 139.313, 138.911, 136.346, 131.132, 129.690, 128.680, 128.187, 127.792, 117.220.

 

Infrared Spectra

1607 cm-1 (imine C=N), 1596 cm-1, 1577 cm-1 (BTD C=N)

 

High-Resolution Mass Spectrometry

Calculated: 494.1565 m/z

Found (M + 1)+: 495.1635 m/z


Lead Reference

Mann, G.; Hartwig, J.; Driver, M.; Fernández-Rivas, C.  Journal of the American Chemical Society 1998, 120 (4), 827-828.

Supplementary Information

Carbon NMR in chloroform (SK34 C NMR.pdf)
Proton NMR in chloroform (SK34 H NMR.pdf)

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Get structure file (.cdx, .sk2, .mol)

Keywords: heterocyclic compounds, imine, transition metal catalysed

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