Anion assisted [4 + 2] cycloaddition reaction via indolo[2,3]-dienolate by reacting 1,2-dimethylindole-3-carboxaldehyde with aromatic nitriles using lithium diisopropylamide in terahydrofuran, a facile and convenient regiospecific route designed and developed for the synthesis of γ-carbolines.

    Abstract
        Graphic abstract
    1 Introduction
    2 Results and discussion
    3 Experimental section
        3.1 General procedure for the synthesis of 3-aryl-5-methyl-[5H]-pyrido[4,3-b]indoles (9a–o)
        3.2 5-Methyl-3-phenyl[5H]pyrido[4,3-b]indole (9a)
        3.3 3-(4′-Methoxyphenyl)-5-methyl[5H]pyrido[4,3-b]indole (9b)
        3.4 3-(3′,4′-Dimethoxyphenyl)-5-methyl[5H]pyrido[4,3-b]indole (9c)
        3.5 5-Methyl-3-(3′,4′,5′-trimethoxyphenyl)[5H]pyrido[4,3-b]indole (9d)
        3.6 3-(4′-N,N-dimethylaminophenyl)-5-methyl[5H]pyrido[4,3-b]indole (9e)
        3.7 8-Methoxy-5-methyl-3-phenyl[5H]pyrido[4,3-b]indole (9f)
        3.8 8-Methoxy-3-{4′-methoxyphenyl)-5-methyl[5H]pyrido[4,3-b]indole (9g)
        3.9 3-{3′,4′-Dimethoxyphenyl)-8-methoxy-5-methyl[5H]pyrido[4,3-b]indole (9h)
        3.10 8-Methoxy-5-methyl-3-(3′,4′,5′ trimethoxyphenyl)[5H]pyrido[4,3-b]indole (9i)
        3.11 3-(4′-N,N-dimethylaminophenyl)-8-methoxy-5-methyl[4,3-b]indole (9j)
        3.12 7-Methoxy-5-methyl-3-phenyl [5H]pyrido[4,3-b]indole (9k)
        3.13 7-Methoxy-3-{4′-methoxyphenyl)-5-methyl[5H]pyrido[4,3-b]indole (9l)
        3.14 3-{3′,4′-Dimethoxyphenyl)-7-methoxy-5-methyl[5H]pyrido[4,3-b]indole (9m)
        3.15 7-Methoxy-5-methyl-3-(3′,4′,5′trimethoxyphenyl)[5H]pyrido[4,3-b]indole (9n)
        3.16 3-(4′-N,N-dimethylaminophenyl)-7-methoxy-5-methyl[4,3-b]indole (9o)
        3.17 1,2-Dimethyl-3-(2′-cyanoethenyl)indole (11a)
        3.18 1,2-Dimethyl-3-(2′-cyanoethenyl)-5-methoxyindole (11b)
        3.19 1,2-Dimethyl-3-(2′-cyanoethenyl)-6-methoxyindole (11c)
    4 Conclusions
    References

• Gopi Reddy Alugubelli(Department of Pharmaceutical Chemistry, SANA College of Pharmacy)
• Sivanadh Musunuri(Department of Chemistry, ANR College)
• Reddymasu Sreenivasulu(Department of Chemistry, JNTU Kakinada)
• Mandava Venkata Basaveswara Rao(Department of Chemistry, Krishna University)