Turpin synthesis

Aromatic denitrocyclizations have been used for many years in some well-known synthetic reactions. Probably the best known example is the Turpin synthesis of phenoxazines and similar synthesis of phenothiazines. The classical setup used usually base-catalyzed reactions in polar protic solvents, very often alcohols. In many cases using polar aprotic solvents was found advantageous. Besides the mentioned influence of the H-bonding, better ionization and lower solvation of the nucleophile are also important. Sf Ar reactions proceed through strongly polarized complexes, which are well soluble and highly polarized in polar aprotic solvents. 

The best-known example of the denitrocyclization reactions is probably the Turpin synthesis of phenoxazines 179 (1891JCS714, 1899CB2601,... 

Tungsten, tricarbonyleyelopentadienylhydrido-reaction with ynamines, 1, 666 Turpin reaction, 3, 1033 Tylophorine occurrence, 4, 478 synthesis, 4, 472, 475 Tylosin... 

Turpin F, Mison P, Sillion B (1996) Synthesis of linear polyimides using Diels-Alder polyaddition. In Feger C, Khojasteh MM, Molis SE (eds) Polyimides trend in materials and applcations (Proceedings of the Fifth International Conference on Polyimides). Society of Plastics Engineers Inc, Hopewell Jet, p 169... 

Ruell, J. A., De Clercq, E., Pannecouque, C., Witvrouw, M., Stup, T. L., Turpin, J. A., Buckheit, R. W., Jr., Cushman, M. Synthesis and Anti-HIV Activity of Cosalane Analogues with Substituted Benzoic Acid Rings Attached to the Pharmacophore through Methylene and Amide Linkers. J. Org. Chem. 1999, 64, 5858-5866. 

One ofthe most elegant syntheses comes from Joseph A. Turpin and Leland O. Weigel. Starting material is 6-methylhept -6-en-2-one, which is as well an intermediate in the ionone synthesis, and can be accessed from isobutene, formaldehyde and acetone. By means of a Sharpless dihydroxylation and acid ring-closure, frontalin is obtained with an enantiomeric excess of60-70 %. [200]... 

Marine diatoms are major contributors to coastal and oceanic primary productivity. Assimilation of nitrate, the predominant limiting nutrient, is usually tightly coupled to photosynthetic carbon fixation however, during darkness or periods of rapid nitrate assimilation, stored carbon reserves are respired for the energetic requirements of the cell and for protein synthesis (Turpin and Weger 1990). 

McLaughlin, J.C., Smith, S.M. (1994) Metabolic regulation of glyoxylate-cycle enzyme synthesis in detached cucumber cotyledons and protoplasts. Planta 195, 22-28 Turpin, D.H., Weger, H.G. (1990) Interactions between photosynthesis, respiration and nitrogen assimilation. 

Smith, R.G., Gauthier, D.A., Dennis, D.T. and Turpin, D.H. (1992) Malate- and pymvate-dependent fatty acid synthesis in leucoplasts from developing castor endosperm., Plant Physiol 98, 1233-1238. 

Tryptophans, synthesis 18, 965 Tungstic acid 18, 142 Turpin phenoxazine ring closure 17, 328... 

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