Cation rearrangement

TiFFENEAU Aminoalcohoi rearrangement Cationic rearrangement (nng enlargement) of 1,2-aminoalcohois by diazotizatlon... 

Type (b) reaction on this rearranged cation (16) will yield more propene (15), while type (a) reaction with water will yield propan-2-ol... 

Desmethylindolactam G (50, R=H, replace zPr by H) was subjected to the same sequence (50 54). The first allylation step succeeded with 52% yield, but the aza-Claisen rearrangement/cationic cyclization gave only 9.5% of the product mixture 52-54 (replace /Pr by H). 

Interestingly, treating (>/4-cyclooctatetraene)Fe(CO)3 with acetyl chloride under Friedel-Crafts reaction conditions yielded unexpectedly222-223 the (>/2,>/3-8-e.x0-acetyl bicy-clo[3.2.1]octadienylium)Fe(CO)3 cation complex, presumably by rearrangement of the intermediate bicyclo[5.1.0]octadienylium isomer (Scheme 8). The structure of the rearranged cation was confirmed from the X-ray crystal structure and from the typical 1,3-cr.ji-allylic products obtained upon nucleophilic reaction with LiAlD4 and NaCN. The nucleophilic reaction of the more bulky iodide occurs, however, on the metal. 

For boron rearrangements, cation-stabilizing groups migrate worst n-alkyl > s-alkyl > t-alkyl... 

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