The hitherto unreported reactions of β-alkoxyvinyl polyfluoroalkyl ketones with ethyl isocyanoacetate and equimolar amounts of potassium-tert-butoxide proceeded mainly in the β-position of the α,β-unsaturated ketones in cases of α-nonsubstituted 1a–e and α-methyl substituted ketones 1g–j. Other α- or β-substituted ketones 1f,k–o gave mainly products 4 of initial attack at the carbonyl carbon. Depending on the solvent, the major products of β-attack do exist in different tautomeric forms. Generally the openchain enol tautomers 5 predominate in the polar DMSO-d(6), while the cyclic γ-hemiaminals 8 are the major tautomers in the less polar CDCl(3). Acid treatment of the latter compounds 8 led to the hitherto unknown ethyl 5-polyfluoroalkyl-pyrrole-2-carboxylates 11 by elimination of formic acid. Catalytic hydrogenation of pyrrole 11a was used for the synthesis of earlier unknown 5-trifluoromethyl proline 16.

The reaction of trifluoroaldol acetal and other polyfluoroalkyl β-ketoacetals with ethyl isocyanoacetate was applied for the preparation of hitherto unknown fluorinated amino acids, cis- and trans-3-CF3/C2F5-prolines as well as trans-3-CF2Br/CF2Cl/CHF2-3-hydroxyprolines.

Diels–Alder reactions of ethyl 3‐benzamido‐2‐oxo‐6‐(trifluoromethyl)‐2H‐pyran‐5‐carboxylate (1a) with electronically different dienophiles, including cyclic enol ethers, cycloalkenes, α,β‐unsaturated ketones, and terminal acetylenes, are useful for the efficient and selective three‐step preparation of trifluoromethyl‐containing aromatic compounds such as 3‐aminobenzoic acid derivatives. We presume that the presence of the trifluoromethyl group is the main factor in determining the regioselectivity of the initial cycloaddition.

Diels—Alder reaction of pyrone (I) with alkoxy alkenes at 120 °C provides the corresponding cycloadducts (III) and (IV).

New δ‐(polyfluoroalkyl)‐δ‐hydroxy‐α‐amino acids were synthesized from the corresponding starting 3‐(benzoylamino)‐6‐(polyfluoroalkyl)‐2H‐pyran‐2‐ones. The key step of the synthesis was the hydrogenation of the pyrone ring. Stereoselectivity and yields depended dramatically on the reaction conditions and the nature of the polyfluoroalkyl group. Various conditions were used for the preparation of both mixtures of diastereomers and pure diastereomers of the target amino acids. The obtained δ‐(polyfluoroalkyl)‐δ‐hydroxy‐α‐amino acids are of interest as analogues of 2‐amino‐5‐hydroxyvaleric acid and glutamic acid.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)