Synthesis, Structure, and Reactivity of N-Indolyl Complexes of the Chiral Rhenium Lewis Acid [(.eta.5-C5H5)Re(NO)(PPh3)]+: Diastereoselective Electrophilic Additions Academic Article uri icon

abstract

  • Reactions of the triflate complex (ƞ5-C5H5)Re(NO)PPh3)OTf) (3) and indolide salts K(NCH═C(R)C═CCH═CHCH═CH) give the N-indolyl complexes (ƞ5-C5H5)Re(NO)(PPh3)-(NCH═C(R)C═CCH═CHCH═CH) (2, R = H/CH3/C2H5 (a/b/c); 71–59% after crystallization). Reactions of 2a,b and HOTf give the indolenine complexes [(ƞ5-C5H5)Re(NO)(PPh3)- (N═CHCH(R)C═CCH═CHCH═CH)]+ TfO- (4+TfO-; a, 93%; b, 77%, (86–92):(14-8) SR,RS/SS,RR Re,C diastereomers). Reaction of 2b and CH3OTf gives [(ƞ5-C5H5)Re(NO)(PPh3)-(N=CHC(CH3)2C═CCH═CHCH═CH)]+TfO- (5+TfO-, 96%). Reactions of 2b and C2H5OTf, and 2c and CH3OTf, give (ƞ5-C5H5)Re(NO)(PPh3)N═CHC(CH3)(C2H5)C═CCH═CHCH═CH)]+ TfO- (6+TfO-, 92–96%; 65:35, 17:83 SS,RR/SR,RS, respectively). Reaction of 2b and [(ƞ5- C5H5)Re(NO)(PPh3)(IC2H5)]+BF4- gives 6+BF4- (93%, 91:9 SS,RR/SR,RS) and (ƞ5-C5H5)Re-(NO)(PPh3)(I) (84%). Reactions of 5+TfO- and CH3MgCl or LiB(C2H5)3H (THF, -80 °C) give addition products (ƞ5-C5H5)Re(NO)(PPh3)(NCH(R)C(CH3)2C═CCH═CHCH═CH) (R ═ CH3 (95:5 SS,RR/SR,RS), H). The latter and HOTf yield indoline complex [(ƞ5-C5H5)Re(NO)- (PPh3)(HNCH2C(CH3)2C═CCH═CHCH═CH)]+,TfO- (9+TfO-, 85%), which when treated with C≡NCH2Ts (60 °C, CHCl3) gives 3,3-dimethylindoline (81%) and [(ƞ5-C5H5)Re(NO)- (PPh3)(C≡NCH2Ts)]+TfO- (14+TfO-, 77%). Reaction of 3 and C≡NCH2Ts also gives 14+TfO- (94%), which is reduced by BH3·THF (THF, reflux) to (ƞ5-C5H5)Re(NO)(PPh3)(CH3) (60%). The crystal structure of 2c, reactions of nonracemic compounds, and rationales for the preceding configurational assignments are also reported. © 1994, American Chemical Society. All rights reserved.

author list (cited authors)

  • Johnson, T. J., Arif, A. M., & Gladysz, J. A.

citation count

  • 18

publication date

  • August 1994