Spiropyrazolines

The spiropyrazohnes obtained from 51 were converted into enantiopure A -pyrazoline-3-carboxylates and 1 -(hydroxyethyl)cyclopropane-1 -carboxylates (128). Those obtained from 54 and 55 were transformed into optically active a-spirocyclopropyllactones and 3-amino-3-(hydroxyethyl)pyrrolidin-2-ones (130). The spiropyrazoline obtained from a chiral propylidene-diketopiperazine and diazomethane was converted into (+)-(lR,25)-l-amino-2-ethyl)cyclopropane-l-carboxylic acid (allocoronamic acid) (135). 

Nitrile imines, generated in situ from the corresponding N-(phenyl)aryIhydra-zonoyl chlorides, react with unsaturated 5(4//)-oxazolones 673 to give the corresponding spiropyrazoline oxazolones 74 647,648,925-92 regioselective... 

TABLE 7.48. OXAZOLONE SPIROPYRAZOLINES FROM 1,3-DIPOLAR CYCLOADDITION REACTION OF UNSATURATED 5(4//)-OXAZOLONES WITH NITRILE IMINES ... 

This curve mimics the 0(t) curve (e.g., Fig. 5B). The optical yield is a maximum at the maximum of the 0 — t curve, i.e., at 63% photodestruction for k < 1,5. Examples are trans-3,5-diphenyl-pyrazoline 15 with Prei( max) = 1.1% [ 332 — 0.058, ee(Tmax) = 3%] or the spiropyrazoline 1 with Prei(Tmax) = 1 7% g = 0.096, ee(Tmax) = 4.3%]. Indeed, most papers published on cpl photochemistry for these reasons deal with asymmetric photodestruction. Balavoine et al. [40] reached 20% ee at 99% destruction for camphor 16 even higher ee of 30% was reached for frawtf-bicylco. Olnonane-S-one 17 [76,77]. Emeis et al. [78] reported that 17 also shows circularly polarized luminescence with gem = 0.035... 

Cycloadditions and condensations as essential tools in spiropyrazoline synthesis 13EMC(63)347. 

In continuing his studies with spiropyrazolines, Durr has obtained the new spirene system (154) and the first spirocyclopropabenzenes (155). ° Photodecomposition of... 

Analogous reactions of acetophenone dimethylhydrazone and acetophenone ethoxycarbonylhydrazone with chromone 130a gave p-hydroxy hydrazone 200 and spiropyrazoline 201, which are also 1,2-adducts. In contrast, acetophenone and... 

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