3.2.5 Attempts to Synthesize 1,2a,3,4a,5,9b-Hexahydrobenzo[g]imidazo[2,1,5-
cdlindolizin-4(2H)-one (3.23).

 We recently reported reaction of succindialdehyde (3.19) with benzotriazole and N-

phenylethylenediamine leading to 1-phenyl-5-(benzotriazol-1-yl)hexahydro-1H-

pyrrolo[1,2-a]imidazole 3.20. The benzotriazolyl group at the 5-position in 3.20 is readily

removed by nucleophilic substitutions with Grignard reagents, allylsilanes, silyl enol

ethers, or triethyl phosphite to furnish novel 1-phenyl-5-substituted-hexahydro-1H-

pyrrolo[1,2-a]imidazoles 3.21 [Nu = alkyl, aryl, allyl and P(O)(OEt)2] (Scheme 3-6).

[00JOC3683] Since chiral diamines 3.11a-c were readily obtained in high yields, our

initial idea intended to use chiral diamine 3.11a instead of N-phenylethylenediamine, in

order to control the two new chiral centers at 5- and 7a-positions. Subsequent treatment

of Bt intermediates 3.22 was supposed to undergo intramolecular cyclizations at the

tethered phenyl group to give 3.23.




 CHOCHO H2N HNPh Bt N NPh Nu- Nu N NPh
 BtH "I
 3.19 3.20 3.21
 11a, BtH

 Ph
 NOE H3 AIC3 H
 ABtI3 N
 Bt N C6H4Me-p N N-C6H4Me-p
 C H5\ /H7a /H7a

 3.22 (de > 99%) 3.23

Scheme 3-6. Attempts to synthesize 1,2a,3,4a,5,9b-hexahydrobenzo[g]imidazo[2,1,5-
 cd]indolizin-4(2H)-one