Azomethineimines cycloaddition with

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 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... 

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... 

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