Cycloadditions V. Tetracyanoethylene Adducts of 1-Carbomethoxyazepines’ John E. Baldwin and Roger A. Smith2
Contribution from the Noyes Chemical Laboratory, University of Illinois, Urbana, Illinois 61803. Received June 22, 1965 The adducts f r o m tetracyanoethylene and I-carbome4 Diels-Alder cyclothoxyazepines arise f r o m 2 6 cycloaddiaddition reactions, rather than f r o m 2 tions as previously suggested. Spin-spin couplings across the H-C-N-C-H system of the adducts 23 of 1.3-1.5 C.P.S. have been found. Carbalkoxynitrenes and carbalkoxycarbenes apparently have quite dissimilar reactivities toward aromatic nuclei.
+
+
Introduction Cycloadditions between a suitable olefin and a cyclic conjugated triene (1) might take a variety of courses. The olefin and triene 1 might give 2 2, 2 4, or 2 6 cycloaddition products (3, 4, 5, or 6), and adducts of type 7, from a Diels-Alder reaction of the valence tautomer 2 of the triene system or from a 2 2 2 cycloaddition3 of olefin and triene 1. For substituted trienes, further structural or stereochemical alternatives for the cycloaddition reaction obtain.
+
+
+
+ +
tion from 1 to give 3 might also have some opportunity for reaction at C-6.
8
A number of cycloaddition reactions between cyclic conjugated trienes and olefins have been reported. Cycloheptatriene,’ 1,3,5-cyclooctatriene,* cyclooctatetraene,g and oxepine’O all give Diels-Alder adducts of type 7. Tropones and tropolones give 2 4 cycloadditions directly to afford products of type 5 . In sharp contrast to these many examples of cycloadditions between olefins and cyclic conjugated trienes which may be concerted is the indication that 1carbethoxyazepine (9) and tetracyanoethylene give a 2 6 cycloaddition product (10).l2
+
+
2
1
0
@
4
3
N&3 7 I
COzCHs 11
5
7
6
Theoretical generalizations based on symmetry arguments and molecular correlation diagrams predict that the thermal 2 4 cycloadditions of 1 or 2 and the thermal 2 2 2 cycloaddition of 1 with olefins may be c ~ n c e r t e d . ~Examples !~ of such reactions are well known. The thermally nonconcerted304processes, involving 2 2 or 2 6 cycloadditions, may not be summarily dismissed as inconsequential alternatives for such reactions. Thermal 2 2 cycloadditions have merited thorough review5 and the bifunctional intermediates (8) involved in such a cycloaddi-
+ + +
+
+
+
(1) Paper IV: J. E. Baldwin and R. H. Greeley, J. Am. Chem. SOC., 87, 4514(1965). (2) Archer Daniels Midland Co. Fellow, 1964-1965. (3) R. Hoffmann and R. B. Woodward, J. Am. Chem. SOC.,87, 2046 (1965). ~.~ __,.
(4) H. C. Longuet-Higgens and E. W. Abrahamson, ibid., 87, 2045 (1965). (5) J. D. Roberts and C. M. Sharts, Org. Reactions, 12, 1 (1962). (6) Cf.P. D. Bartlett, L. K. Montgomery, and B. Seidel, J. Am. Chem. Soc., 86, 616 (1964); L. K. Montgomery, K. Schueller, and P. D. Bart-
Baldwin, Smith
We have synthesized a series of adducts from substituted 1-carbomethoxyazepines and tetracyanoethylene. The n.m.r. spectra of the adducts reveal that they are 8,8,9,9-tetracyano-2-carbomethoxy-2-azabicyclo[3.2.2]nona-3,6-dienes (11). The spectra also afford new data on “long-range” spin-spin couplings. Some information on the selectivity of the postulated carboxynitrene intermediate in reactions with aromatic compounds was obtained. These three topics, structural assignments for the azepine-tetracyanoethylene lett, ibid., 86, 622 (1964); P. D. Bartlett and L. K. Montgomery, ibi d. 86, 628 (1964). (7) K. Alder and G. Jacobs, Chem. Ber., 86, 1528 (1953); however, see G. Kresze and G. Schulz, Tetrahedron, 12, 7 (1961). (8) A. C. Cope, A. C. Haven, Jr., F. L. Ramp, and E. R. Trumbull, J . Am. Chem. SOC.,74, 4867 (1952). (9) R. Huisgen and F. Mietzsch, Angew. Chem., 76, 36 (1964); Angew. Chem. Infern. Ed. Engl., 3, 83 (1964); E. Vogel, H. Kiefer, and W. R. Roth, Angew. Chem., 76, 432 (1964). (10) E. Vogel, W. A. Boll, and H. Giinther, Tetrahedron Leffers,No. 10, 609 (1965). (11) Cf.P. L. Pauson, Chem. Rev., 55, 9 (1955). (12) K. Hafner, Angew. Chem., 75, 1041 (1963); Angew. Chem. Infern. Ed. Engl., 3, 165 (1964).
Tetracyanoethylene Adducts of I-Carbomethoxyazepines
4819
Table I. Tetracyanoethylene-Azepine Adducts" Yield of adduct,
Azepine precurser Bromobenzene Chlorobenzene Fluorobenzene Benzene Toluene Anisole p-Xylene
-
Anal.,
IC-
Z
Structure
M.P.,~"C.
36 ( 2 X ) d 30 28 (3X) 38 (3X) 15 34 27
23a 23b 23c 23d 23e 23f 18
167-169 152.5-154.5 168-170 165-167 128-130 156-158 172-173.5
Formula CI~&N~O~ Cx4HsNsOzCI' Ci4HsNbOzF Ci4HeN50z Ci 5H11N 6 0 2 CiJLxN503 CI~HI~NSOZ
H
-----. 7
Calcd.
Found
Calcd.
Found
-N Calcd.
B46.95 ~~ 53.60 56.57 60.21 61.43 58.25 62.53
46.94 53.65 56.56 60.22 61.62 58.25 62.36
2.25 2.57 2.71 3.25 3.78 3.58 4.20
2.05 2.60 2.69 3.24 3.86 3.49 4.37
19.55 22.32 23.56 25.08 23.88 22.64 22.79
I
Found 19.34 22.55 23.32 24.76 23.81 22.77 22.06 22.20 21.71
a Prepared from a n aromatic precurser, methyl azidoformate, and tetracyanoethylene. b N o attempt has been made to improve yields by altering reaction conditions or initial concentrations. From toluene; uncorrected. 2X signifies after two recrystallizations. * Calcd. : mol. wt., 358; Br, 22.31; Found: mol. wt., 376 (osmometricinacetone); Br, 21.93. f Calcd.: C1, 11.30; Found: C1, 11.13.
Table 11. Coupling Constants and Chemical Shifts in Tetracyanoethylene-Azetine Adducts Formula
Compd.
X
x ; ; ;& ;& )(
(7)
H
H(i)
(2)
CO,CH,
= = =
Br Cl
X F X = H X=CHa X=OCHa
23a 23b 23c 23de 23ef 23fg
18h
-Coupling constants," c.p.s.--. J45 J34 J17 J d J13d 9.0 9.1 9.2 8.8 9.0 9.2
8.9 9.2 9.2 8.8 9.2 9.3
7.7 8.0 7.5 7.5 8.4
1.8 1.9 1.6 1.3 1.4 2.0
Js6
J67
J34
J35
7.7
1.6
1.6
1.1
1.5 1.5 1.4 1.5 1.3
Chemical shifts,ba% H-4 H-5
I
H-1
7
H-3
H-7
3.96 3.87 3.80i 4.05 4.11 3.91
2.93 2.93 2.92 2.92~0.15 3.07 3.01
4.68 4.65 4.66 4.78 4.78 4.75
5.70 5.75 5.70 6.08 6.20 6.07
3.07 3.26 3.80j 3.0&0.15 3.72 4.55
4.38
3.37
h
6.84
h
C02CH, _ _ _ _ _ _ _ _ ~ ~ ~
~~~
~~~
~~
~~
Spectra of all adducts were obtained from All coupling constantsrange from 1 0 . 1 to 0.3 C.P.S.in estimated error, except where noted. 30% &-acetone solutions except that of 18 which was determined as a 30% solution in deuteriochloroform; chemical shifts are relative to a tetramethylsilane internal standard, and are estimated accurate to rt0.03 p.p.m. c Jab= 0 was demonstrated by spin decoupling H-3 and Jx3= 1.5 was demonstrated by spin decoupling H-1 and H-3 of adduct 23b. e JW = 8.1 1 0 . 6 , J56 = 8.1 + 0.6, J M = H-5 of adduct 23b. H-6 T 3.67; CH3(4), CH3(7) 7 7.30 and 8.10. Carbo1.2 C.P.S. ; H-6 7 3.45. f Methyl at C-6; T 7.86, J6, = 1.6 C.P.S. 0 OCH3 T 6.19. methoxy 7 6.12 rt 0.01 for all adducts. 7 Center of a complex multiplet. a
adducts, "long-range" n.m.r. spin-spin coupling consystem, stants in the 2-azabicyclo[3.2.2]nona-3,6-diene and carbomethoxynitrene reactivity toward aromatic substrates, are now considered in turn. Structures of Adducts Thermal13 or photochemica114-16decomposition of an azidoformate in the presence of an aromatic substrate leads, probably through electrophilic attack of a carboxynitrene on the benzenoid system, to l-carboxyazepines. When methyl azidoformate was decomposed at 120 O in bromobenzene, l-carbomethoxybromoazepine was obtained. Although this product showed but a single OCH, absorption in the n.m.r. (at 7 6.20) it may still have been a mixture of two or three isomers. Treatment of the 1-carbomethoxybromoazepine(s) with tetracyanoethylene gave a 1 : l adduct of m.p. 167169". The same adduct was obtained more conveniently by decomposing methyl azidoformate at 120" in the presence of bromobenzene and tetracyanoethylene. (13) R. J. Cotter and W. F. Beach, J . Org. Chem., 29, 751 (1964). (14) K. Hafner and C. Konig. Angew. Chem., 75, 89 (1963); Angew. Chem. Intern. Ed. Engl., 2 , 96 (1963). (15) W. Lwowski, T. J. Maricich, and T. W. Mattingly, Jr., J . Am. Chem. Soc.. 85, 1200 (1963). (16) I
