Nonracemic syn-selective aldol reactions with a second-generation vinylogous urethane lithium enolate

Journal of Organic Chemistry

Volumn 61, Issue 10, 1996, Pages 3226-3227

  Schlessinger, Richard H ^a   Li, Yu Jang ^a,b   Von Langen, Derek J ^a,c  

^a UNIVERSITY OF ROCHESTER   (United States)

^b Research Rensselaer Polytechnic Institute   (United States)

^c MERCK RESEARCH LABORATORIES   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0000437647     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo960324z     Document Type: Article

References (7)

1. Sehlessinger, R. H.; Iwanowicz, E. J.; Springer, J. P. J. Org. Chem. 1986, 51, 3070
2. Schlessinger, R. H.; Iwanowicz, E. J. Tetrahedron. Lett. 1987, 28, 2083.
3. Schlessinger, R. H.; Williard, P. G.; Tata, J. R.; Adams, A. D.; Iwanowicz, E. J. J. Am. Chem. Soc. 1988, 110, 7901.
4. Enders, D.; Kipphardt, H.; Gerdes, P.; Brenak-Valle, L. J.; Bhushan, V. Bull. Soc. Chim. Belg. 1988, 97, 691.
5. Under typical conditions, the vinylogous urethane derived from isopropylmethylamine 16 provides 17 with 3:1 syn:anti selectivity. This experimental observation is consistent with the structural findings (X-ray) found for the enolate derived from vinylogous urethane 1, as well as for the observation that the vinylogous urethane derived from pyrrolidine is exclusively anti-selective, whereas the vinylogous urethanes derived from tert-butylmethylamine and diisopropylamine are exclusively syn-selective.
6. This, of course, assumes that the reactive species in solution is that depicted in structures 8 and 3. The validity of these enolate structures as the reactive intermediates in solution, particularly as aggregated species, is currently being examined.
7. For a leading reference on the consideration of transition states for the aldol condensation, see: Bernardi, A.; Gennari, C.; Goodman, J. M.; Volker, L.; Paterson I. Tetrahedron 1995, 51, 4853.