P(PhCH2NCH2CH2)3N: An Efficient Lewis Base Catalyst for the Synthesis of Propargylic Alcohols and Morita—Baylis—Hillman Adducts via Aldehyde Alkynylation.

Proazaphosphatrane P(PhCH2NCH2CH2)3N (1a) is an efficient catalyst for the addition of aryl trimethylsilyl alkynes to a variety of aromatic, aliphatic, and heterocyclic aldehydes in THF at room temperature. The reaction conditions are mild and employ a low catalyst loading (ca. 5 mol %). Only propargylic alcohols were isolated in good to excellent isolated yields when electron-rich, electron-neutral, heterocyclic, and aliphatic aldehydes were employed, whereas β-branched Morita−Baylis−Hillman (MBH) type adducts were isolated with electron-deficient aromatic aldehydes after conventional acid hydrolysis of the TMS ether products. Alkynes containing heterocyclic and aromatic groups bearing electron-withdrawing or -donating substituents underwent clean addition to cyclohexanecarboxaldehyde and to electron-rich aromatic aldehydes to give propargylic alcohols in excellent isolated yields. β-Branched Morita−Baylis−Hillman (MBH) type adducts were isolated when electron-deficient aromatic aldehydes were employed. ...