P(PhCH2NCH2CH2)3N: An Efficient Lewis Base Catalyst for the Synthesis of Propargylic Alcohols and Morita−Baylis−Hillman Adducts via Aldehyde Alkynylation
摘要:
Proazaphosphatrane P(PhCH2NCH2CH2)(3)N (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 beta-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. beta-Branched Morita-Baylis-Hillman (MBH) type adducts were isolated when electron-deficient aromatic aldehydes were employed. Reaction pathways to both types of products are proposed.
Quaternary and Tertiary Carbon Centers Synthesized via Gallium-Catalyzed Direct Substitution of Unfunctionalized Propargylic Alcohols with Boronic Acids
作者:Clayton P. Donald、Amy Boylan、Truong N. Nguyen、Po-An Chen、Jeremy A. May
DOI:10.1021/acs.orglett.2c02612
日期:2022.9.23
secondary and tertiary propargylic alcohols with organoboronic acids via C–C bond formation, and GaCl3 effectively synthesized all-carbonquaternary propargylic centers. These catalysts performed the substitution at carbons bearing alkyl substituents, which has been problematic for other systems. Highly hindered carbon stereocenters were thus produced, including quaternary centers bearing doubly ortho-substituted