Jesús M. de los Santos

2H-Azirines as Synthetic Tools in Organic Chemistry

The versatility and the high synthetic potential including the asymmetric syntheses of 2H-azirines as valuable precursors for the preparation of a wide range of polyfunctional acyclic and cyclic compounds, is discussed.

PREPARATION, PROPERTIES AND SYNTHETIC APPLICATIONS OF 2H-AZIRINES A REVIEW

INTRODUCTION .............................................................................................................................. 221 I . STRUCTURAL PROPERTIES OF W-AZIRLNES .................................................................. 222 1 . Molecular Orbital Calculations and Geometry ..................................................................... 222 2 . Spectroscopic Properties .......................................................................................................... 223 a) Nuclear Magnetic Resonance Spectroscopy ......................................................................... 223

Regioselective alkylation reactions of hydrazones derived from phosphine oxides and phosphonates. Synthesis of phosphorus substituted 1-amino-pyrrolones, pyridinones and pyrroles

Abstract Functionalized hydrazones derived from phosphine oxides or phosphonates were obtained from azaenolates of hydrazones and alkyl halides. The regioselectivity of alkylation of α-phosphorylated hydrazones can be controlled by phosphorus moiety. α-Alkylated compounds were used for the synthesis of heterocycles such as 1-aminopyrrol-2-ones, 1-amino-3,4-dihydropyridin-2-ones and 1-aminopyrroles containing phosphinyl or phosphoryl substituents.

An effective strategy for the preparation of (α,β-unsaturated hydrazones and pyrazole derivatives. Synthetic applications of β-functionalized phosphorus compounds.

Abstract β-Enehydrazino phosphonium salts 3 as web as β-hydrazano phosphine oxides 6 and phosphonates 7 are obtained from hydrazines, propargylphosphonium salts 2 and phosphorylated allenes 4 and 5. β-Functionalized compounds 3,6 and 7 are used for the synthesis of α,β-unsaturated hydrazones 1, pyrazoline 14 and pyrazole derivative 15.

Asymmetric synthesis of 2H-aziridine phosphonates, and α- or β-aminophosphonates from enantiomerically enriched 2H-azirines

Abstract A simple and efficient method for asymmetric synthesis of 2 H -azirine-2-phosphonates 6 is described. The key step is a base-mediated Neber reaction of p -toluenesulfonyloximes 4 derived from phosphonates. Triethylamine 5 , alkaloids 7 and solid-phase bound achiral 8 or chiral amines 9 are used. Reduction of 2 H -azirines 6 with sodium borohydride in ethanol gives cis -aziridine-phosphonates 10 . Ring opening of aziridines 10 and 11 leads to the formation of enantiomerically enriched β- 12 and 14 and α-aminophosphonates 13 and 15 .

Synthetic Applications of Intramolecular Aza-Wittig Reaction for the Preparation of Heterocyclic Compounds

A review focused on recent advances in intramolecular aza-Wittig reaction of phosphazenes with several car- bonyl or analogous compounds is reported. Phosphazenes afford intramolecular aza-Wittig reaction with different groups within the molecule as aldehydes, ketones, esters, thioesters, amides, anhydrides and sulfimides. One of the most impor- tant applications of this reaction is the synthesis of a wide range of heterocyclic compounds, ranging from simple mono- cyclic compounds to complex polycyclic and macrocyclic systems.

An efficient and general strategy for the synthesis of 4-phosphorylated pyrazoles from β-hydrazono phosphine oxides

Abstract A simple and efficient synthesis of aminopyrazoles substituted with a phosphino oxide and sulphide groups in the 4-position 1 is described. The key step is a regioselective addition of lithiated β-hydrazonophosphine oxides 2 to isocyamates and isothiocyanates to give functionalized amides 3 and 7 . Subsequent cyclization of 3 with phosphorus oxychloride in the presence of triethylamine afforded pyrazoles derived from phosphine oxides 1 and phosphine sulphides 8 . Substituted heterocycles 1 can also be obtained in “one pot” reaction from phosphine oxides 2 when these compounds are metallated followed by addition of isocyanates and phosphorus oxychloride.

An efficient strategy for the regioselective synthesis of 3-phosphorylated-1-aminopyrroles from β-hydrazono phosphine oxides and phosphonates

Abstract An easy strategy for the synthesis of 1-aminopyrroles substituted with a phosphine oxide or phosphonate group in the 3-position is described. The key step is the 1,4-conjugate addition of the enamine to the 4-phosphorylated 1,2-diazabuta-1,3-diene 3 and heterocyclisation to give substituted 1-aminopyrroles 9. Basic hydrolysis of pyrroles 9 afforded 3-phosphinoyl-1-aminopyrroles 11. Similarly substituted 3-phosphinoyl-1-aminopyrroles 10 can also be obtained from acetylacetone and 1,2-diazabuta-1,3-diene 3.

An improved and effective method for the preparation of α,β-unsaturated oximes and isoxazole derivatives

Abstract β-Functionalized oximes derived from phosphine oxides 5 , phosphonates 8 and phosphonium salts 10 are easily obtained by simple addition of hydroxylamine compounds 2 to substituted allenes 3 and 6 or to propargylphosphonium salt 9 . These oximo derivatives are used for the synthesis of α,β-unsaturated oximes 1 , and isoxazole derivatives 13 .

Reactions of Conjugate Phosphinyl- and Phosphonyl-Nitroso Alkenes with Enamines. Preparation of N-Hydroxypyrrole Derivatives†

The synthesis of highly functionalized N-hydroxypyrrole derivatives by the formal [3+2] cycloaddition reaction of enamines and nitroso alkenes derived from phosphine oxides and phosphonates is reported. Intermediate phosphorylated nitrones, whose formation can be explained by a conjugate addition of enamines to phosphorylated nitroso alkenes and formation of the five-membered heterocycles, are isolated.