LETTER
based on a tartrate substituent, see: Loh, T.-P.; Wang, R.-B.;
Sim, K.-Y. Tetrahedron Lett. 1996, 37, 2989. (b) Tartrate
boronic esters, however, are considered moderately
activated by the electron-withdrawing ester groups.
(3) For a review on remote stereoinduction, see: Mikami, K.;
Shimizu, M.; Zhang, H.-C.; Maryanoff, B. E. Tetrahedron
2001, 57, 2917.
Self-Activation and 1,8-Stereoinduction
479
2 H), 7.18 (br s, 1 H), 7.10 (m, 1 H), 6.43 (d, J = 17 Hz, 1 H),
6.25 (dd, J = 17 Hz, 10.2 Hz, 1 H), 5.78 (d, J = 10 Hz, 1 H).
13C (CDCl3, 75 MHz): = 164.0, 140.2, 132.8, 129.5, 126.9,
124.4, 120.3. Pinacol para-boronoanilide 8: 1H NMR
(Acetone-d6, 300 MHz): = 7.75 (AB, J = 9 Hz, 2 H), 7.68
(AB, J = 9 Hz, 2 H), 6.46 (dd, J = 17 Hz, 10 Hz, 1 H), 6.34
(dd, J = 16 Hz, 3 Hz, 1 H), 5.70 (dd, J = 10 Hz, 3 Hz, 1 H),
1.31 (s, 12 H); 13C NMR (Acetone-d6, 100 MHz): = 164.1,
142.8, 136.3, 136.2 (broad weak signal, C-B), 132.7, 127.4,
119.2, 84.3, 25.2; 11B NMR (Benzene-d6, 64 MHz): = 30.8;
IR (CH2Cl2 cast, cm–1): 3303 (m, N-H), 3102 (w, Csp2-H),
2978 (m, Csp3-H), 1667 (s, C=O), 1635 (s, C=C alkyl), 1593
(s, C=C aromatic), 1361 (vs, B-O), 860 (m, p-sub Ar);
HRMS (EI): m/z calcd for C15H20NO311B: 273.15363, found:
273.15381. (b) Hegedus, L. S.; Allen, G. F.; Olsen, D. J. J.
Am. Chem. Soc. 1980, 10, 3583.
(4) For a recent example of remote asymmetric induction using
chiral boronates, see: Sailes, H. E.; Watts, J. P.; Whiting, A.
J. Chem. Soc., Perkin Trans. 1 2000, 3362.
(5) (a) All compounds reported herein were obtained in a high
state of purity and exhibited spectral data (NMR, MS) in
accord with proposed structures. Characterization data for
dienophile substrates 4, 6, 8: Pinacol ortho-boronoanilide 4:
white solid, mp: 168–170 °C; 1H NMR (Acetone-d6, 400
MHz): = 10.34 (br s, 1 H), 8.06 (m, 1 H), 7.67 (d, J = 8 Hz,
1 H), 7.37 (m, 1 H), 7.10 (apparent t, J = 8 Hz, 1 H), 6.38 (m,
2 H), 5.82 (dd, J = 7 Hz, 5 Hz, 1 H), 1.38 (s, 12 H); 13C NMR
(Acetone-d6, 100 MHz): = 164.1, 143.6, 136.0, 135.9,
132.2, 131.8, 131.7, 127.9, 127.8, 124.6, 124.5, 119.0, 84.1,
(6) ortho-Aminophenylboronic acid can be obtained from
various commercial sources or prepared according to: (a)
Nitration: Seaman, W.; Johnson, J. R. J. Am. Chem. Soc.
1931, 53, 711. (b) Hydrogenation: Groziak, M. P.; Ganguly,
A. D.; Robinson, P. D. J. Am. Chem. Soc. 1994, 116, 7597;
the para-aminophenylboronic acid was obtained from
Combi-Blocks.
(7) X-ray crystallographic data have been deposited to the
Cambridge Crystallographic Data Centre (file number:
CCDC 166880).
84.0, 25.6, 25.5; 13C NMR (Benzene-d6, 100 MHz):
=
163.2, 145.3, 136.4, 133.1, 132.8, 125.8, 123.4, 119.6, 83.9,
24.8. A very slight peak duplication effect, ca. 0.05 ppm,
was observed for arene carbons in acetone. This may be due
to a slow competing effect from this coordinating solvent.
11B NMR (Benzene-d6, 64 MHz): = 30.1; IR (CH2Cl2 cast,
cm–1): 3316 (m, N-H), 3058 (w, Csp2-H), 2970 (s, Csp3-H),
1646 (s, C=O), 731 (s, o-sub Ar); HRMS (EI): m/z calcd for
C15H20NO311B: 273.15363; found: 273.15376. Acrylanilide
6:5b 1H NMR (CDCl3, 300 MHz): = 7.58 (m, 2 H), 7.31 (m,
(8) For an example of internally coordinated alpha-
acetamidomethylboronate, see: Matteson, D. S.; Michnick,
T. J.; Willet, R. D.; Patterson, C. D. Organometallics 1989,
8, 726.
Synlett 2002, No. 3, 477–479 ISSN 0936-5214 © Thieme Stuttgart · New York