Snieckus’ synthesis

Scheme 32. Snieckus synthesis of anhydrolycorinone (continued next page).

Bisagni and team (96) have also reported a synthesis of the related 5H-pyrido[4,3-6]benzo[/]indolo-6,l 1-quinone ring system (e.g., 200) (Scheme 34). Using a modification of the Watanabe-Snieckus synthesis (97) of ellipticine, the... 

Lithiation of both A/-phenyl- and 0-phenyl-urethanes has been reported. The ortho lithiadon of /V-r-bu-toxycaibonylaniline and subsequent addition to carbonyls, nitriles and several other electrophiles was first reported by Muchowski in 1980. In some cases the adduct cyclized by attacking the urethane carbonyl. Typical examples are shown in Scheme 17. Lithiation of an /V-r-butoxycarbonylaniline derivative served as one of two directed lithiation steps in Snieckus synthesis of anthramycin (17 Scheme 18). Treatment of phenothiazines with 2 equiv. of butyllithium affords an A(,o-dilithium species, but reaction with electrophiles occurs at both sites. Katritzky has shown that the sequence of N-lithiadon, car-bonation and o-lithiation protects the nitrogen from alkylation (Scheme 19). ... 

S1079 M. Gharpure, A. Stoller, F. Bellamy, G. Fimau and V. Snieckus Synthesis, 1991, 1079. 

A soln. of 2-methyl-l,2,3,4-tetrahydropyrimido[l,6-a]indole in aq. 50%-acetic acid heated 4 hrs. on a steam bath -> 2-methyl-l,2,3,4-tetrahydro-5H-pyrido[4,3-b]-indole. Y 80%. Also reverse rearrangement s. K. S. Bhandari and V. Snieckus, Synthesis 1971, 327. 

---