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18.1.2.2.3 Method 3: Addition of Thiocyanates or Selenocyanates to Aldehydes and Alkene Double Bonds

DOI: 10.1055/sos-SD-018-00002

Wu, Y.-Q.Science of Synthesis, (20051831.

Aryl selenocyanates react rapidly at room temperature with aldehydes in the presence of tributylphosphine to give (arylselanyl)acetonitriles 60 in excellent yields (Scheme 18). Mechanistically, the reaction involves the instantaneous formation of a selanylphosphonium cyanide 59 on mixing tributylphosphine and the aryl selenocyanate; the cyanide then reacts rapidly with the aldehyde. The resulting cyano oxyphosphonium salt undergoes aryl selenide displacement of tributylphosphine oxide to give (arylselanyl)acetonitrile 60.[‌37‌] The one-carbon homologation of an aldehyde to a nitrile possessing an α-arylselanyl substituent implies a synthetically useful reaction that permits a variety of transformations. For example, cyclopentanecarbaldehyde is converted directly into the α,β-unsaturated nitrile 61 through a selenoxide elimination in a high overall yield under mild conditions. Likewise, the reaction between aryl thiocyanates and arylaldehydes leads to aryl(arylsulfanyl)acetonitriles in good to excellent yields, as illustrated by the synthesis of the sulfanyl nitrile 62 (Scheme 18).[‌38‌]

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