Azomethineimines

The 3 + 2-cycloaddition of 1,2-dithiophthalides with nitrilimines yields benzo[c]thio-phenespirothiadiazoles regioselectively. The azomethineimines isoquinolinium-iV-aryllimide and A-(2-pyridyl)imide readily undergo 1,3-dipolar cycloaddition with electron-deficient dipolarophiles, dimethyl fumarate and dimethyl maleate, to yield tetrahydropyrazolo[5,l-a]isoquinolines in high yield. ° The 1,3-dipolar cycloadditions of electron-poor 1,3-dipoles, bicyclic azomethine ylides (27), with ( )-l-A,A-dimethylaminopropene to yield cycloadducts (28) and (29) are examples of non-stereospecific cycloadductions (Scheme 9). The synthesis of protected... 

The azomethineimine 244 obtained from A-phenyl azodicarboximide and 9-diazofluorene, adds DMAD to give the spiro compound 245.170... 

The three-nitrogen azimine 1,3-dipolar system in benzocinnolinium ylides26 undergoes cycloaddition with acetylenedicarboxylic esters to give azomethineimines, presumably derived from the initial A4-triazoline 1,3-cycloadduct by an electrocyclic ring opening (Scheme 8).2 7... 

The palladium [Pd(Ph3)4]-catalysed 3 + 3-cycloaddition of trimethylenemethane with azomethineimines produced hexahydropyridazine derivatives under mild conditions (40 °C).171 The Lewis acid-catalysed formal oxa-[3 + 3]-cycloaddition of a,f+ unsaturated aldehydes with 6-methyl-4-hydroxy-2-pyrone, 1,3-diketones, and viny-logous silyl esters yielded a variety of pyrones at room temperature.172 Croton-aldehyde has been converted to 6-hydroxy-4-methylcyclohex-l-enecarboxaldehyde by an enantioselective 3 + 3-cycloaddition catalysed by proline. This methodology was used in the synthesis of (—)-isopulegol hydrate, (—)-cubebaol, and (—)-6-hydroxy-4-methylcyclohex-l-ene-1-methanol acetate, an intermediate in the total synthesis of the alkaloid magellanine.173... 

Azomethines, electrochemical heterocyclization 89MI13. Azomethineimines, cycloaddition reactions 86MI5. 

Azoalkenes, transformation into N-heterocycles 86OPP301. Azomethineimines, synthesis of N-heterocycles from 78CLY921. 

Trifluoromethyl derivatives of azomethine imines are effective 1,3-dipoles in reactions with unsaturated compounds. Thus, RCH = CHR type olefins and azinehexafluoroacetone react to form azomethineimine, transformed into 1/7-3-pyrazoline (75JCS(P1)538, 79T389) (Scheme 26). Heating the latter with AIBN leads to trifluoromethyl derivatives of pyrazole (82JFC(19)437) (Scheme 26). 

In contrast to product formation by thermal extrusion of molecular nitrogen from the 4-phosphapyrazoIines (446), photoproduct formation results in deep-seated skeletal rearrangements. Irradiation of the 5-alkylidene derivatives yields the azomethineimines (447), which are spectroscopically detectable and thermally stable in solution. Continued irradiation converts (447) into (449) which opens to give (451). In the case of the 5-arylidene derivative, the ring-contracted product (4 ) is converted to primary photoproduct (450) which aromatises on standing to give (452). ... 

Condensation of addehydes with N-acyl-V -alkylhydrazines affords an incipient azomethineimine capable of cycloaddition to suitable double bonds. The value of the synthesis is indicated by reactions in Scheme 16. Reaction with benzaldehyde shows a marked regioselectivity. Other interesting dipolar additions are shown in Scheme 17. The interm iacy of a diazacyclopenta-dienone in the decomposition of (59) is clearly shown by the trapping experiments. Also reported are adducts of tetracyanoethylene with 3,6-dialkyl-azepines and the Cope rearrangement of the pyrroline oxide (60) to give... 

RECENT ADVANCES IN CATALYTIC ASYMMETRIC 1,3-DIPOLAR CYCLOADDITIONS OF AZOMETHINEIMINES, NITRILE OXIDES, DIAZOALKANES, AND CARBONYL YLIDES... 

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