Aminobenzonitrile compounds

As a second example we consider, briefly, twisted intramolecular charge transfer in aminobenzonitrile compounds.This is a donor-acceptor system (Figure 3.30). The S2 excited state of this system is a charge-transfer state involving the transfer of an electron from the nitrogen atom to the benzene ring. The Si excited state is a locally excited state, involving the excitation of... 

Substituted 4-aminoquinazolines 847 can be prepared by combining 2-aminobenzonitriles 846 with nitriles under basic conditions <2000JME2227, 2005SC2481>, and a microwave-assisted procedure is now available that enables these compounds to be produced very efficiently <2000TL2215>. 

Derivatives of l,2-dihydro-l,3,2-diazaborines are prepared from 2-aminobenzonitrile or 2-aminobenzamides. Compounds (147) were obtained from 2-aminobenzonitrile (148) and boron trihalides (equation 12). However, it was stated that dichlorophenylborane or... 

A similar rapid microwave one-pot synthesis of substituted quinazolin-4-ones was also reported, which involved cyclocondensation af anthranilic acid, formic acid (or an orthoester) and an amine under solvent-free conditions (Scheme 3.37)61. A complimentary approach was adopted to synthesise 4-aminoquinazolines in very good yields, involving the reaction of aromatic nitrile compounds with 2-aminobenzonitrile in the presence of a catalytic amount ofbase (Scheme 3.38)62. The reactions were performed in a domestic microwave oven and required only a very short heating time. A microwave-assisted synthesis of a variety of new 3-substituted-2-alkyl-4-(3H)-quinazolinones using isatoic anhydride, 2-aminobenzimidazole and orthoesters has also been described (Scheme 3.38)63. 

Aminobenzonitriles 17 react with Grignard reagents to give the intermediate iminium salt 20, which can be readily trapped in situ by carbonyl compounds (e.g., acid chlorides, anhydrides, formates, carbonates, and oxalates) or phosgeniminium chlorides and cyclized to quinazolines. With this method various 2-unsubstituted quinazolines, 2,4-disubstituted quinazolines, and quinazolines with certain functional groups (e.g., COjEt, NMe ) in the 2-position are readily available. 

Figure 2. Formulas of selected D-A compounds which contain 4-dialkylamino group as an electron donor and reveal dual fluorescence behaviour. Top /)-cyano-A,A-dimethylaniline (I, CDMA) and its model derivatives p-cyano-2,A,A-trimethylaniline (II), p-cyano-2,6,A.A-tetramethylaniline (III, CTMA)./)-aminobenzonitrile (IV, ABN) and l-ethyl-2,3-dihydro-indole-5-carbonitrile (V. BIN). Middle 4-(dimethylamino)pyrimidine (VI), 4-(diethylamino)pyrimidine (VTI), 4-(dimethylamino)-5-methylpyrimidine (VIII), 4-(diethylamino)-5-methylpyrimidine (IX) and 4-(dimethylamino)-pyridine (X). Bottom methyl 4-(dimethylamino)benzoate (XI, DMAMB), ethyl 4-(dimethylamino)benzoate (XII, DMAEB), p-(dimethylamino)-benzaldehyde (XIll) and />-(dimethylamino)acetophenone (XIV).

A study of all the stages in the synthesis of 4-aminoquinazolines from isatoic anhydride, via anthranilamide and o-aminobenzonitrile, made possible the preparation of these compounds by a one-pot synthesis. The anhydride was treated with ammonia in dimethylformamide, nitrogen was then bubbled through the solution to remove excess of ammonia, phosphoryl chloride was added and heated at 40°-60°C for conversion into the nitrile, and finally the respective amine was added to yield the 4-(substituted-amino)-quinazolines in 44-79% yields. ... 

Bogert and Hand used 2-aminobenzonitrile derivatives to generate 2-styrylquinazoline-4(3//)-one analogues. Treatment of 2-aminobenzonitrile with 3-phenyl-acryloyl chloride followed by oxidative ring closure, gave the desired quinazolinone in 29% yield. 6-Chloro derivatives of this class of compounds, independently prepared by Hamel and co-workers (not shown), were shown to have growth inhibitory activity against leukemia cells. 

Figure 3.30 Acceptor and donor components of aminobenzonitrile (ABN) compounds. The first two excited states correspond to a local excitation of the benzene ring (LE) and a charge transfer (CT) from the amino group into the benzene ring.

Figure 3.31 TICT co-ordinate in aminobenzonitrile (ABN) compounds. The TICT (twisted intermolecular charge transfer) coordinate corresponds to the angle between the donor and the acceptor in Figure 3.30. Population of S2 in a partition at a conical Intersection into CT and LE minima and dual fluorescence.

Figure 3.32 VB structures for aminobenzonitrile (ABN) compounds. VB structures I and ii correspond to A + B and A B in Fig. 5. Ill and IV are charge-transfer configurations where an electron has been transferred to the benzene ring. Adapted from Gomez eta . ° ...

---