SYNTHESIS, STRUCTURE, AND REACTIVITY OF N-INDOLYL COMPLEXES OF THE CHIRAL RHENIUM LEWIS-ACID [(ETA-5-C5H5)RE(NO)(PPH3)]+ - DIASTEREOSELECTIVE ELECTROPHILIC ADDITIONS

Reactions of the triflate complex (eta5-C5H5)Re(NO)(PPh3)(OTf) (3) and indolide salts K(NCH=C(R)C=CCH=CHCH=CH) give the N-indolyl complexes (eta5-C5H6)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 [(eta5-CrH5)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 [(eta5-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 [(eta5-C5H5)Re(NO)(PPhs)(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 [(eta5-C5H5)Re(NO)(PPh3)(IC2H5)]+BF4- gives 6+BF4- (93%,91:9 SS,RR/SR,RS) and eta5-C5H5)Re(NO)(PPh3)(I) (84%). Reactions of 5+TfO- and CH3MgCl or LiB(C2H5)3H (TBF, -80-degrees-C) give addition products (eta5-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 [eta5-C5H5)Re(NO)-(PPh3)(CHC(CH3)2C=CCH=CHCH=CH)]+TfO- (9+TfO-, 85%), which when treated with C=NCH2Ts (60-degrees-C, CHCl3) gives 3,3-dimethylindoline (81%) and [(eta5-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, reflux) to (eta5-CrH5)Re(NO)(PPh3)(CH3) (60%). The crystal structure of 2c, reactions of nonracemic compounds, and rationales for the preceding configurational assignments are also reported.