Organic Division Problem Set Nov 9th, 2012
Rearrangements leading to spirocycles
Shehani Mendis
Stereoselective Synthesis of Functionalized Spiro[4.5]decanes by Claisen Rearrangement of Bicyclic
Dihydropyrans
Nakazaki, A.; Miyamoto, H.; Henmi, K.; Kobayashi, S. Synlett 2005, 9, 1417
Claisen rearrangement of dihydropyrans occur via a boat like transition state…..
Büchi, G.; Powell, J. E. Jr. J. Am. Chem. Soc. 1970, 92, 3126
Question 1 Provide the structures of 1 and 2 in this one pot synthesis.
(Claisen Rearrangement)
Answer
Highly Diastereoselective One-Pot Synthesis of Spirocyclic Oxindoles through Intramolecular Ullmann
Coupling and Claisen Rearrangement
Kobayashi, S. Angew. Chem. Int. Ed. 2006, 45, 2274
Answer
Intramolecular Ulmann-type coupling
Reaction conditions: substrate (0.5 mmol), CuCl (10 mol%), 2-aminopyridine (10 mol%), DME (10 mL), NaOMe/MeOH (25 wt%; 2.0 equiv), Ar, sealed tube. Reaction time and temperature were not optimized for each substrate.
Kobayashi, S. Angew. Chem. Int. Ed. 2006, 45, 2274
Hypervalent Iodine oxidation of N-Acyltryamines
Kita, Y.; J. Org. Chem. 1991, 56, 435-438
Question 2 Provide a mechanism leading to the product.
Oxidative Prins-Pinacol Tandem Process Mediated by a Hypervalent Iodine Reagent
Beaulieu, M. A.; Guerard, K. C.; Maertens, G.; Sabot, C.; Canesi, S. J. Org. Chem. 2011, 76, 9460
Formation of Aldehyde and Acetal Functionalities
Beaulieu, M. A.; Guerard, K. C.; Maertens, G.; Sabot, C.; Canesi, S. J. Org. Chem. 2011, 76, 9460
Stereoselectivity Issues Following the Conformational Equilibriums
(R)
Beaulieu, M. A.; Guerard, K. C.; Maertens, G.; Sabot, C.; Canesi, S. J. Org. Chem. 2011, 76, 9460
Oxidative Prins-Pinacol Tandem Reaction with Alkynes
Beaulieu, M. A.; Guerard, K. C.; Maertens, G.; Sabot, C.; Canesi, S. J. Org. Chem. 2011, 76, 9460
Question 3
Propose a mechanism for the formation of 3.
Domino reaction leading to spiro cyclohexadienone lactones
Answer
Fujioka, H.; Komatsu, H.; Nakamura, T.; Miyoshi, A.; Hata, K.; Ganesh, J.; Muraia, K., Kita, Y. Chem Commun. 2010, 46, 4133
Experimental Results:
Question 4
Name the name reactions involved and provide a mechanism for the following reaction.
Sequential WagnerMeerwein Migrations and theSynthesis of Spirocyclic Cyclopentenones
Nazarov Cycloadduct
1,2-hydride migration
1,2-carbon migration
Huang, J.; Lebœuf, D.; Frontier, A. J. J. Am. Chem. Soc. 2011, 133, 6307–6317
Huang, J.; Lebœuf, D.; Frontier, A. J. J. Am. Chem. Soc. 2011, 133, 6307–6317
bridged intermediate…..
Huang, J.; Lebœuf, D.; Frontier, A. J. J. Am. Chem. Soc. 2011, 133, 6307–6317
Question 5 Provide the structure of 4, and the mechanism leading to 4.
Answer
Kido, F.; Abiko, T.; Kato, M. J. Chem. Soc. Perkin Trans. 1 1992, 229-233