Complex of Diphenylcyclopropenone with Substituted Acetic Acid and Formic Acid N a r e n d r a S . S r i d h a r a Department of Chemistry, The University, Leicester LE 1 7RH, England and Rajendra Singh Department of Chemistry, Meerut College, Meerut [U. P.], India (Z. Naturforsch. 32 b, 453-454 [1977]; received March 1, 1976) Diphenylcyclopropenone, Bromoacetic Acid, Trifluoroacetic Acid, Benzoylformic Acid, NMR Reaction of diphenylcyclopropenone with bromoacetic acid, trifluoroacetic acid and benzoylformic acid leads to crystalline complexes. Condensation reactions of diphenylcycloprope­ forms crystalline complex with bromoacetic acid, none with active methylene compounds are known trifluoroacetic acid and benzoylformic acid. to be catalyse’d by borontrifluoride etherate1. Cyclo- Reaction of diphenylcyclopropenone was carried propenone-Lewis acid complex could be inter­ out in boiling cyclohexane with equimolar quantity mediates, in view of the well known tendency of of bromoacetic acid, trifluoroacetic acid and benzoyl­ forming Lewis acid complex of ketones2 and formic acid and afforded crystalline adduct of activation of diphenylcyclopropenone with hydrogen diphenylcyclopropenone. The NMR spectrum of chloride3 or triethyloxoniumtetrafluoroborate4. the complex 3 in CDCI 3 solution [60 MHz, <5 = 7.63 Y o s h id a and M iy a h a r a prepared BF3 and SbCls- m, 6H, meta + para) and 7.92 (m, 4H, ortho)] showed complex quantitatively by adding BF 3 0 E t2 to a downfield shift of the aromatic protons relative to diphenylcyclopropenone in acetic acid and SbCls to respective absorptions of diphenylcyclopropenone7. diphenylcyclopropenone in methylene chloride both Assignment of two characteristic strong bands, at room temperature5. A g r a n a t and C o h e n de­ ca. 1850 and 1630 cm-1 of diphenylcyclopropenone scribed the preparation of diphenylcyclopropenone has been discussed8-9. K r e b s 10 has suggested to complexes with dichloroacetic acid, phenylacetic invert this assignment and to consider the 1630 cm-1 acid, diphenylacetic acid and cyanoacetic acid6. We band as the stretching mode of the carbonyl group, wish to report that diphenylcyclopropenone also whilst the 1850 cm-1 band is said to be characteristic of the disubstituted cyclopropene system. Diphenyl­ Requests for reprints should be sent to Dr. N a r e n ­ cyclopropenone showed the band at 1344 cm-1 dra S. Sridhara, Department of Chemistry, The University, Leicester LEI 7BH, England. which is probably due to C-CO-C skeleton vibration. Table. The NMR spectra of diphenylcyclopropenone-complex (in ppm). <5 <5 <5 Ö Compound (COOH) (ortho*) (meta + para*) c h 2 Diphenylcyclopropenone 7.90 7.50 Diphenylcyclopropenone-bromoacetic acid 11.00 7.92 7.63 3.86 Diphenylcyclopropenone-trifluoroacetic acid 13.22 7.98 7.62 Diphenylcyclopropenonebenzoylformic acid 10.89 7.96 7.46 * (The center of the corresponding multiplets of AB2C2 systems.) The 19F NMR spectrum of diphenylcyclo­ propenone-trifluoroacetic acid complex showed a singlet at 11.57 ppm using H5C6CF3 as external reference. 454 N. S. Sridhara-R. Singh • Complex of Diphenylcyclopropenone On the other hand, diphenylcyclopropenone com­ 1584 (m), 1564 (m), 1365 (s), 1268 (s), 1176 (m), plexes had a peak at 1365 cm-1, which could be 1102 (w), 1020 (w), 980 (m), 922 (w), 896 (m), 768 (s), 688 (s) and 640 (m). C-CO-C vibrational band. The mass spectrum of each complex contained a signal at m/e 178 re­ Found C 59.02 H3.61, Calcd C 59.14 H 3.80. presenting the diphenylacetylene. The following two complexes were prepared in a Reaction scheme: similar manner: h5c 6s ,c 6h5 h5c 6 ^ / C6h5 C = C 4. Diphenylcyclopropenone-trifluoroacetic acid complex ♦ BrCH2COOH -------— 0 m.p. 57-58 °C (yield 0.08 g, ca. 50%); II I 0 ----- H-0-C-CH2Br IR spectrum (Nujol): 3400 (vs), 1816 (vs), 1772 (w), 2 3 1680 (w), 1596 (s), 1580 (w), 1560 (w), 1490 (w), 1376 (m), 1338 (w), 1312 (w), 1200 (s), 1185 (s), Experimental 1140 (s), 1020 (w), 992 (w), 972 (s), 922 (w), 808 (m), 776 (s), 760 (s) and 680 (vs). 1. Preparation of diphenylcyclopropenone 9 2. Preparation of bromoacetic acid u Found C 63.23 H 3.24, 3. Preparation of diphenylcyclopropenone- Calcd C 63.74 H 3.46. bromoacetic acid complex (3) 5. Diphenylcyclopropenone-benzoylformic acid 0.103 g (0.0005 mole) of diphenylcyclopropenone complex (1) and 0.07 g (0.0005 mole) of bromoacetic acid were dissolved in 20 ml cyclohexane and the reaction m.p. 78-79 °C (yield 0.12 g, ca. 70%) mixture was refluxed for 15 min and gradually IR spectrum (Nujol): 3392 (vs). 2512 (m), 2444 (m), cooled to room temperature and then cooled in ice- 1810 (vs), 1712 (s), 1685 (s), 1604 (s), 1584 (s), bath. The complex 3 crystallized from the solution. 1365 (s), 1308 (m), 1260 (m), 1208*(s), 1184 (s), The colourless crystals filtered off and washed with 1168 (m), 1080 (w), 1028 (w), 1008 (w), 980 (s). 944 (w), 928 (w), 848 (m), 768 (s), 750 (s), 688 (s), cyclohexane and dried (yield 0.065 g; ca. 60%), m.p. 36-37 °C. The IR spectrum (in Nujol medium) 632 (m) and 620 (m). showed the following absorptions: 3400 (vs), 2610 (w), Found C 77.01 H 4.30, 2500 (w), 1848 (s), 1804 (m), 1720 (s), 1600 (s), Calcd C 77.52 H 4.52. 1 Y. K i t a h a r a and M. 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