Highly Regioselective α-Addition of Alkynyl and Alkenyl Grignard Reagents to 1-Alkoxycarbonylpyridinium Salts and Its Application to Synthesis of 1-Azabicycloalkanes and (±)-Solenopsin A
Nucleophilic addition of a variety of alkynyl and alkenyl Grignardreagents to 1-methoxycarbonylpyridinium chloride takes place at the α-position in a highly regioselective manner to give 2-substituted 1-methoxycarbonyl-1,2-dihydropyridines exclusively, while, with alkyl Grignardreagents, a lack of the regioselectivity is observed. These results may be explained by the HSAB principle. The high α-regioselectivity
SYNTHESIS OF<i>cis</i>- AND<i>trans</i>-2,6-DIALKYLATED PIPERIDINES THROUGH HIGHLY REGIOSELECTIVE α-ALKYNYLATION OF PYRIDINIUM SALTS AND ITS APPLICATION TO SYNTHESIS OF (±)-SOLENOPSINE A
Reactions of N-methoxycarbonyl-2-alkylpyridinium salts with alkynyl Grignard reagents give exclusively 2,6-disubstituted 1,2-dihydropyridines, from which cis- and trans-2,6-dialkylated piperidines can be derived selectively. Consequently, (±)-solenopsine A is efficiently synthesized by this sequence.
通过 N-甲氧基羰基-2-烷基吡啶鎓盐与炔基格氏试剂的反应,可以得到 2,6-二取代的 1,2-二氢吡啶,并从中选择性地衍生出顺式和反式 2,6-二烷基哌啶。因此,(±)-solenopsine A 可以通过这种方法高效合成。
NAKAZONO, YUTAKA;YAMAGUCHI, RYOHEI;KAWANISI, MITUYOSI, CHEM. LETT., 1984, N 7, 1129-1132