Metal-free Reductive Coupling of Biphenyl Tosylhydrazones with Phenols or Benzyl Alcohols

Background: The 4-benzyl biphenyl scaffold represents an important structural element widely used in optoelectronic materials and bioactive compounds, including a variety of antihypertensive drugs and prostate cancer agents. Therefore, the construction of 4-benzyl groups incorporating this structural feature with cheap and readily available starting materials is of great scientific interest. Methods: In this paper, the reductive coupling of biphenyl-4-carbonyl compounds derived from tosylhydrazones with phenols or benzyl alcohols under metal-free reaction conditions is described. Results: Various 4-benzyl biphenyl ether compounds, representing an important structural element in organic synthesis, could be obtained in moderate to good yields. Conclusion: The catalytic system presented here enables the use of easily accessible starting materials and may be employed on a wide variety of substrates with good functional group tolerance.