text:  The <unk> <unk> reaction ( often referred to as simply the <unk> <unk> ) is a chemical reaction used in organic chemistry for the synthesis of <unk> . The reaction is typically divided into classical and modern variants , depending on the reagents and substrates employed . It was originally discovered by Ivan Nikolaevich <unk> ( 1906 – 1957 ) in 1941 while studying the rearrangements of allyl vinyl ketones . 
  