8453 Scheme I
7
8
I CN R’ 9
0
I
CN
reaction of 1 (R = C ~ H Swith ) tolan, and a mixture melting point test of the two samples showed no depression. p-Nitrostilbene has been caused to react with 1 (R = C6H5)in D M F solution for 18 hr at loo”, and 2-(1isoquinolyl)-3-p-nitrophenyl-4,5-diphenylpyrrole was isolated in 45% yield. The structure of the product was proved by its conversion via the amino derivative and its diazonium salt to be the known“ 2-(l-isoquinolyl)-3-p-anisyl-4,5-diphenylpyrrole. The reaction of p-methoxystilbene with 1 (R = C6H5) under the same conditions as specified for the corresponding reaction of p-nitrostilbene gave 2-(isoquinolyl)-3-panisyl-4,5-diphenylpyrrolein 18 yield and 2 4 l-isoquinolyl)-4-p-anisyl-3,5-diphenylpyrrole in 9 yield. The reaction of 1 (R = CsH,) with p-methoxytolan in refluxing D M F solution for 24 hr gave, in 12 % yield, a mixture of 1,3-diphenyl-2-p-anisylpyrrolo[2,1 -a]isoquinoline and 2,3-diphenyl-l-p-anisylpyrrolo[2,I-alisoquinoline in a ratio of 1 :2. There was also obtained, in 5.4 % yield, a mixture of 2-( l-isoquinolyl)-3,5-diphenyl4-p-anisylpyrrole and 2-(isoquinolyl)-3-p-anisyl-4,5-diphenylpyrrole in a ratio of about 35:65. Under the same reaction conditions, 1 (R = C6HS)and p-nitrotolan gave, in 31 yield, a mixture of 2,3-diphenyl-l-p. nitrophenylpyrrolo[2,1 -a]isoquinoline and 1,3-diphenyl2-p-nitrophenylpyrrolo[2,l-a]isoquinolinein a ratio of about 2 : 1. Also, there was obtained, in 7.3 % yield, a mixture of 2-(l-isoquinolyl)-4-p-nitrophenyl-3,5-diphenylpyrrole and 2-(l-isoquinolyl)-3-p-nitrophenyl-4,5-diphenylpyrrole in approximately a 1 : 1 ratio. The formation of mixtures of isomers in most of these reactions indicates that the initial condensation reactions involve essentially synchronous formation of two new covalent bonds in each ring closure, as indicated in previous publications. 4-6 The structures of all of the products cited above were proved by unambiguous methods. Acknowledgment. This work was supported in pari by grants from the National Institutes of Health and the National Science Foundation. William E. McEwen,* Paul E. Stott, Charles M. Zepp Department of Chentistry, Unicersity of Massachusetts Amlierst, Massachusetts 01002 Receioed July 19, 1973
R 10
12
figurations of the respective energy profiles hold true when an alkene is used as the substrate. Thus, under conditions whereby the reactions are forced to completion, alkynes mainly form products of type 12, and alkenes form products of type 10. An independent and unambiguous synthesis of 12 (R = CsH5) has been achieved. The lithium salt of 1-benzylisoquinoline was caused to react with 2-(crbromobenzyl)-2-pheny1-1,3-dioxolane(the ethylene glycol ketal of desyl bromide), and the mixture of reaction products was treated with polyphosphoric acid. A small quantity (ca. 2%) of 10 (R = C6H5)was isolated from the reaction mixture. Its ir and nmr spectra were identical with those of the product obtained by the
Correlation between Deuterium and Carbon-13 Relaxation Times. A Convenient Means to Determine the Mechanism of 13C Relaxation and 2H Quadrupole Coupling Constants Sir : The dominant contribution to I3C magnetic relaxation comes from the l3C-IH dipole-dipole interaction, except for very small molecules or rapidly rotating methyl groups where spin-rotation interaction has also to be considered. Scalar interaction and chemical shift anisotropy usually do not contribute significantly to the 13C relaxation of protonated If (1) (a) T. C. Farrar and E. D. Becker, “Pulse and Fourier Transform NMR,” Academic Press, New York, N. Y., 1971 ; (b) G. C. Levy and G. L. Nelson, “Carbon-13 Nuclear Magnetic Resonance for Organic Chemists,” Wiley-Interscience, New York, N. Y.,1972. (2) (a) G. C. Levy and G. L. Nelson, J . Amer. Chem. Soc., 94, 4897 (1972); (b) G. C. Levy, 3. D. Cargioli, and F. A. L. Anet, ibid., 95, 1527 (1973).
Communications to the Editor
8454 Table 1. Comparison of Measured 13C Spin-Lattice Relaxation Times with Those Calculated from *H Relaxation Times, and Evaluation of Quadrupole Coupling Constants -Spin-lattice
relaxation times (Tl) (set)_--__-_ _______ 1 3 c
N,N-Dimethylformamide Acetic acid Cyclohexane Phenylacetylene Benzene Toluene Nitrobenzene
C H I (cis) CHs (trans) CHO CH 3 CH, =CH CH CHa Ca-H Cy-H
2H
Calc&,b
Obsd
3.04 1.62 0.95 1.46f 1.47' 0.25 1.52 5.04 0.58 0.39
20.2 10.7 18.9 9.1 14.6 7.8 33.9 33.4 13.0 8.7
17.@ 10.5c 19.5c 9.@ 17.OC 9.3c 29.3c 16.3d 6.gd 4.8d
Temp, "C 25 25 25 35 36 38 38 38 38
38
Ref 2a 2a 2a 10b 2b 2b 2b 2b 2b 2b
Quadrupole coupling constant -----(e2qQ/fi, kHz --Calcde Obsd Kef 160 168 173 176 183 254 172
168 i. 10 174 =t2 215 5 186 i 1 . 6
+
g
h i j
Corresponding to temperature 30". * Quadrupole coupling constants used: 170 kHz for sp3, 180 kHz for sp2, and 215 kHz for sp. Degassed samples. Undegassed samples. Estimated error 10%. G l a d ' s data, ref 9. 0 M. de Graca, C. Dillon and J. A. S. Smith, J . Chem. SOC.,Faraday Tram. 2, 2183 (1972). J. C. Rowell, W. D. Phillips, L. R. Melbya, and M. Panar, J . Chem. Phys., 43, 3422 (1965). i P. Pykko, Ann. Uniu. Turku, Ser. A , 88,93 (1966). j P. L. Olympia, Jr., I. V. Wei, and B. M. Fung, J. Chm. Phys., 51, 1610 (196 ),
'
more than one mechanism contributes to the relaxation of a given 13C nucleus, the dipole-dipole contribution can be estimated by measurement of the nuclear Overhauser enhancements3 In contrast to 13C and 'H the only significant contribution to the relaxation of 2H (D) arises from the motional modulation of the interaction between the quadrupole moment and the electric field gradient at the n ~ c l e u s . ~Since both 2H and 13C relaxation comes from intramolecular interactions, a comparison of the corresponding 'H and 13C relaxation times should provide an alternative means of estimating the contribution to 13Crelaxation arising from interactions other than dipole-dipole, Furthermore, for those cases where the 13C relaxation time has been shown to be dominated by the dipoledipole interaction, a comparison of the corresponding 2H and 13Crelaxation times provides a new method for calculating the quadrupole coupling constant.jS6 The 2H spin-lattice relaxation times were measured on a Varian XL- 100 spectrometer by the inversion-recovery method' using a 180°-t-900 pulse sequence. The deuterium relaxation time T1('H) is related to the effective correlation time T~ of the molecular reorientation as follows4 l/T1 ('H) = 3 ( e ' q Q / f i ) ' ~ ~ / S (1) where e z q Q / h is the deuterium quadrupole coupling constant. The 13C spin-lattice relaxation time Tl ( T) due to the dipole-dipole relaxation is given by8 1/T1 ("c)= NhZy~Z')'~2Y--6?c (2) where N is the number of hydrogens attached to the corresponding carbon, yc and Y H are the magnetogyric ratios for 13Cand 'H, respectively, and r is the distance (3) I
