Imanol Tellitu

A general and efficient PIFA mediated synthesis of heterocycle-fused quinolinone derivatives

Abstract A new application of the hypervalent iodine reagent phenyliodine(III)bis(trifluoroacetate) (PIFA) has been developed for the construction of a series of N, O, S-containing heterocycle-fused quinolinone derivatives in a general and efficient way. An alternative approach to the formation of these novel tricyclic heterocycles by a PIFA mediated aryl–heteroaryl coupling reaction is also presented.

Novel applications of hypervalent iodine: PIFA mediated synthesis of benzo[c]phenanthiridines and benzo[c]phenanthridinones

A short and efficient access to benzo[c]phenanthridines and phenanthridinones is achieved by the action of phenyliodine(III)-bis(trifluoroacetate) (PIFA) on properly substituted benzylnaphthylamines and naphthylbenzamides, respectively. This reagent promotes a non-phenolic oxidative biaryl coupling process, the key step of the synthesis. A study of the electronic and steric requirements of the substrates is carried out since, in some cases, dimerization processes prevail over intramolecular cyclization. A mechanistic proposal is also included.

A Simple Route to New Phenanthro- and Phenanthroid-Fused Thiazoles by a PIFA-Mediated (Hetero)biaryl Coupling Reaction

An application of the PIFA-mediated [PIFA: phenyliodine(III) bis(trifluoroacetate)] biaryl coupling reaction is presented and extended to the formation of heterobiaryl connections. A preliminary study of the scope and limitations of this procedure was carried out in the synthesis of phenanthroids 11 from a series of phenethyl-substituted heterocycles 10. It was observed that in some cases a competitive dimerization process took place. It was also found that the coupling step could be efficiently extended to a larger number of examples if an aromatic ring were situated fused to the 1,2-diarylethane skeleton, as in 23 and 30. The synthesis of a series of 4,5-diarylthiazoles 23a−g was therefore carried out to explore the electronic requirements and the regioselectivity of the PIFA-mediated non-phenolic coupling reaction. When the same procedure was applied to aryl-heteroarylthiazoles 30, a series of phenanthroid-fused thiazoles 31 was obtained in good overall yields. To the best of our knowledge, no oxidative aryl-heteroaryl coupling reaction of this type had previously been reported. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

A new and practical PIFA-promoted olefin amidohydroxylation: six- versus five-membered ring formation

A novel access to the isoindolinone and isoquinolin-2-one skeletons from adequately substituted aromatic precursors is described. The key intramolecular cyclization step was performed by the action of phenyliodine(III)bis(trifluoroacetate) (PIFA) on the corresponding vinyl or allyl substituted N-(p-methoxyphenyl)benzamide derivatives leading to the heterocyclic compounds through 5-exo-trig and 6-exo-trig processes, respectively.

A simple enzymatic synthesis of (3S,4R)-(+)-4-hydroxy-3-phenyltetrahydroisoquinolines

Abstract An efficient versatile method is presented for the stereospecific synthesis of (+)-4-hydroxy-3-phenyltetrahydroisoquinolines 11 and 12 using (R)-arylcyanohydrins as the chiral starting material. From this asymmetric core, the synthetic process proceeds with development of the S absolute stereochemistry for the phenyl group at C-3 and the R configuration at C-1 of the target heterocycle. As the protective group protocol allows the stereospecific deprotection at C-4, (3S,4R)-(+)-4-hydroxy-3-phenyltetrahydroisoquinolines have been prepared using this process.

An alternative approach towards novel heterocycle-fused 1,4-diazepin-2-ones by an aromatic amidation protocol

The synthesis of new 1,4-diazepin-2-one derivatives starting from glycine or alanine aminoacids is presented. The key cyclization step includes the PIFA mediated formation of N-acylnitrenium ions and their subsequent intramolecular trapping by an (hetero)aromatic ring. The so-promoted aromatic amidation process takes place without loss of enantiomeric purity when optically pure methoxyamide precursors are employed.

An intramolecular PIFA-mediated metal-free allylic oxycarbonylation reaction and its application to the preparation of furopyrimidinones.

The preparation of a series of furo[3,4-d]pyrimidinones by an unprecedented PIFA-mediated intramolecular allylic oxycarbonylation reaction developed on 5-carbamoyl-substituted Biginelli adducts is presented. The construction of the fused lactone by a metal-free C-H activation process, without the need of an additional functionalization step, is featured in the present work.

The amine exchange/biaryl coupling sequence: a direct entry to the phenanthro[9,10-d]heterocyclic framework

Abstract Novel phenanthro[9,10- d ]pyrimidines and phenanthro[9,10- d ][1,2]oxazoles are regioselectively prepared by the application of a straightforward synthetic pathway, starting from new o , o ′-dihalogenated and non-halogenated 4,5-diarylpyrimidines and 4,5-diarylisoxazoles, respectively, prepared via a tandem amine exchange/heterocyclization of diarylenaminones. A comparative study of biaryl coupling methodologies provides two highly efficient, complementary procedures to accomplish the final coupling step: an intramolecular Stille–Kelly stannylation/coupling of halogenated diarylpyrimidines and diarylisoxazoles, and a PIFA-mediated non-phenolic oxidative coupling of the corresponding non-halogenated substrates. In addition, other alternative approaches to the same target tetracyclic systems are also examined.

Regioselective diarylation of ketone enolates by homogeneous and heterogeneous catalysis: synthesis of triarylethanones☆

A novel, one-step approach to 1,2,2-triarylethanones is achieved by an efficient palladium-catalyzed α,α-diarylation of commercially available acetophenones. After assaying an array of experimental conditions, two convenient procedures, which avoid ortho-arylation side reactions, are chosen to perform the target regioselective diarylation. The former protocol is based on the use of such a simple homogeneous system as Pd(OAc)2/PPh3/Cs2CO3, and the latter one employs a commercially available polymer-anchored catalyst, FibreCat™ 1026.

Silicon-mediated isoquinoline synthesis: preparation and stereochemical characterization of 4-hydroxy-3-phenylisoquinolines

Abstract The silicon-mediated synthesis of 4-hydroxy-6,7-dimethoxy-3-phenylisoquinoline derivatives is reported. The described procedure implies synthetically useful yields and a high degree of stereoselectivity.