A New Ring Expansion Reaction of 1-Acyl-2-vinylpiperidine and 1-Acyl-2-Vinylpiperazine via Aza-Claisen Rearrangement of Amide Enolate

REFERENCES

• Tsunoda , T. , Sasaki , O. and Ito , S. 1990 . Tetrahedron Lett. , 31 : 727
   Google Scholar
• Ito , S. and Tsunoda , T. 1990 . Pure & Appl. Chem. , 62 : 1405
   Google Scholar
• Tsunoda , T. , Sakai , M. , Sasaki , O. , Sako , Y. , Hondo , Y. and Ito , S. 1993 . Tetrahedron Lett. , 34 : 3297
   Google Scholar
• Tsunoda , T , Tatsuki , S. , Shiraishi , Y. , Akasaka , M. and Ito , S. 1993 . Tetrahedron Lett. , 34 : 3297
   Google Scholar
• Tsunoda , T. and Ito , S. 1994 . Synth. Org. Chem. , 52 : 113 For recent review, see
   Google Scholar
• Edstrom , E. D. 1991 . J. Am. Chem. Soc. , 113 : 6690
   Web of Science ®Google Scholar
• Edstrom , E. D. 1991 . Tetrahedron Lett. , 32 : 5709
   Web of Science ®Google Scholar
• Vedejs , E. and Gingras , M. 1994 . J. Am. Chem. Soc. , 116 : 579
   Google Scholar
• Tsuda , T. , Kiyoi , T. and Saegusa , T. 1990 . J. Org. Chem. , 55 : 3388
   Google Scholar
• Treatments of 1-acyl-2-vinylazacycles with sec-Buli, KHMDS or NHMDS provided much lower yields than those with LHMDS.
   Google Scholar
• Use of benzene, xylene or dioxane provided relatively lower yield. Decane is less convenient solvent than tolune although it affords the same yield as tolune.
   Google Scholar
• Spectral data for lactam 2c as a representative rearranged product: IR (neat) 3320, 1660 cm−1; 1HNMR (CDCl3, 400 MHz) δ 5.97–5.95 (m, 1H),5.39–5.31 (m, 2H), 3.81 (t, 1H, J = 2.9 Hz), 3.67–3.59 (m, 1H), 3.29 (s, 3H), 2.81 (dd, 1H, J = 13.4, 8.1 Hz), 2.42 (br d, 1H, J = 11.7 Hz), 2.28–2.21 (m, 1H), 2.18–2.13 (m, 1H), 1.88 (ddd, 1H, J = 15.7, 7.8, 7.8 Hz), 1.82–1.76 (m, 1H), 1.67–1.63 (m, 1H), 1.49–1.40 (m, 1H), 1.24–1.15 (m, 1H); 13C NMR (CDCl3, 400MHz) δ 171.5, 136.1, 124.6, 85.1, 57.8, 39.6, 35.9, 32.7, 29.6, 28.9; HRMS Calcd. for C10H17NO2 183.1259, found 183.1263.
   Google Scholar
• Bartlett , P. A. , Tanzella , D. J. and Barstow , J. F. 1982 . J. Org. Chem. , 47 : 3941
   Google Scholar
• Gould , T. J. , Balestra , M. , Wittman , M. D. , Gray , J. A. , Rossano , L. T. and Kallmerten , J. 1987 . J. Org. Chem. , 52 : 3889 and references cited therein
   Google Scholar
• Burke , S. O. , Fobare , W. F. and Pacofsky , G. J. 1983 . J. Org. Chem. , 48 : 5221
   Google Scholar
• The coupling constants between two olefinic protons were determined by decoupling studies.
   Google Scholar
• The chair-chair-like transition state of the amide enolate is favored over the chair-boat-like transition state due to the repulsions between N-alkyl groups and the eclipsed allyic hydrogens of the chair-boat-like transition state.1a Among the chair-chair-like transition states such as transition state A-D, transition states C and D are ruled out due to the preferred formation of Z-amide enolate1a,11 and the aza-Claisen rearrangement proceeds through the energetically favorable transition state A to give E-olefin.
   Google Scholar
• At present, ring expansions of other ring-sized 2-vinylazacycles by aza-Claisen rearrangement of amide enolate are not satisfactory or afford a trace amount of the desired products. Studies on ring expansion of 2-vinylaziridine, 2-vinylazetidine and 2-vinylpyrrolidine are in progress.
   Google Scholar
• Welch , J. T. and Eswarakrishnan , S. 1985 . J. Org. Chem. , 50 : 5909
   Google Scholar