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