Benzophenone imine

Benzophenone imine
Names
	IUPAC name Diphenylmethanimine
Identifiers
CAS Number	1013-88-3;
3D model (JSmol)	Interactive image;
ChemSpider	120561;
ECHA InfoCard	100.103.715
EC Number	600-205-0; 440-870-2;
PubChem CID	136809;
UNII	EJJ21NA7VI;
CompTox Dashboard (EPA)	DTXSID10870832 ;
	InChI InChI=1S/C13H11N/c14-13(11-7-3-1-4-8-11)12-9-5-2-6-10-12/h1-10,14H Key: SXZIXHOMFPUIRK-UHFFFAOYSA-N;
	SMILES C1=CC=C(C=C1)C(=N)C2=CC=CC=C2;
Properties
Chemical formula	C13H11N
Molar mass	181.238 g·mol−1
Hazards
	GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H315, H319, H335
Precautionary statements	P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Benzophenone imine is an organic compound with the formula of (C₆H₅)₂C=NH. Benzophenone imine is widely used as a reagent for the protection of primary amines, and the starting materials to synthesize aniline.^[1]

Synthesis

Benzophenone imine is available via the addition of MeOH to the complex of a nitrile and a Grignard reagent or the reaction between benzophenone and ammonia.

Synthesis via Grignard-nitrile complexes

The first report about the preparation of ketimines involved Grignard-nitrile complexes followed by careful hydrolysis, which is known as Moureu-Mignonac ketimine synthesis.^[3] Then Pickard and Tolbert improved the preparation by using methanol in the addition of Grignard-nitrile complexes.^[2]

Synthesis via benzophenone and ammonia

In 1988, A. G. Guimanini discovered a new route to synthesize benzophenone imine via a reaction using benzophenone ammonia. A chemical pure-grade ammonia gas is added to a benzophenone solution, forming Ph₂C=NH₂⁺. After sodium hydroxide pellets are added to the solution, the Ph₂C=NH₂⁺ is neutralized, generating the expected benzophenone imine.^[4]

Applications

Protecting group for primary amines

Primary amines can be protected benzophenone imine, and the protected amines are stable in flash chromatography.^[5]

Amination of aryl halides

Buchwald-Hartwig amination is a very important kind of reaction for coupling aromatic halide and amine to form carbon-nitrogen bonds with the help of palladium-involved catalysts. In order to obtain anilines, ammonia is required in this reaction. However, ammonia can bind to palladium tightly, which makes the normal Buchwald-Hartwig reaction unavailable. In 1997, Buchwald et. al found that benzophenone imine can be used as an ammonia-equivalent and solve the above limitations.^[1]

References

^ ^a ^b ^c Wolfe, John P.; Åhman, Jens; Sadighi, Joseph P.; Singer, Robert A.; Buchwald, Stephen L. (1997-09-08). "An Ammonia Equivalent for the Palladium-Catalyzed Amination of Aryl Halides and Triflates". Tetrahedron Letters. 38 (36): 6367–6370. doi:10.1016/S0040-4039(97)01465-2. ISSN 0040-4039.
^ ^a ^b Pickard, P. L.; Tolbert, T. L. (December 1961). "An Improved Method of Ketimine Synthesis". The Journal of Organic Chemistry. 26 (12): 4886–4888. doi:10.1021/jo01070a025. ISSN 0022-3263.
^ Moureau-Mignonac Ketimine Synthesis. Hoboken, NJ, USA: John Wiley & Sons, Inc. 2010-09-15. pp. 1988–1990. doi:10.1002/9780470638859.conrr446. ISBN 9780470638859. {{cite book}}: |journal= ignored (help)
^ Verardo, G.; Giumanini, A. G.; Strazzolini, P.; Poiana, M. (1988). "Ketimines From Ketones and Ammonia". Synthetic Communications. 18 (13): 1501–1511. doi:10.1080/00397918808081307.
^ O'Donnell, Martin J. (2001-04-15). Benzophenone Imine. Chichester, UK: John Wiley & Sons, Ltd. doi:10.1002/047084289x.rb031. ISBN 978-0471936237. {{cite book}}: |journal= ignored (help)

[:2-1] Wolfe, John P.; Åhman, Jens; Sadighi, Joseph P.; Singer, Robert A.; Buchwald, Stephen L. (1997-09-08). "An Ammonia Equivalent for the Palladium-Catalyzed Amination of Aryl Halides and Triflates". Tetrahedron Letters. 38 (36): 6367–6370. doi:10.1016/S0040-4039(97)01465-2. ISSN 0040-4039.

[:0-2] Pickard, P. L.; Tolbert, T. L. (December 1961). "An Improved Method of Ketimine Synthesis". The Journal of Organic Chemistry. 26 (12): 4886–4888. doi:10.1021/jo01070a025. ISSN 0022-3263.

[:1-3] Moureau-Mignonac Ketimine Synthesis. Hoboken, NJ, USA: John Wiley & Sons, Inc. 2010-09-15. pp. 1988–1990. doi:10.1002/9780470638859.conrr446. ISBN 9780470638859. {{cite book}}: |journal= ignored (help)

[4] Verardo, G.; Giumanini, A. G.; Strazzolini, P.; Poiana, M. (1988). "Ketimines From Ketones and Ammonia". Synthetic Communications. 18 (13): 1501–1511. doi:10.1080/00397918808081307.

[5] O'Donnell, Martin J. (2001-04-15). Benzophenone Imine. Chichester, UK: John Wiley & Sons, Ltd. doi:10.1002/047084289x.rb031. ISBN 978-0471936237. {{cite book}}: |journal= ignored (help)

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