Synthesis of enantioenriched homopropargylic alcohols through diastereoselective SE' additions of chiral allenylstannanes to aldehydes
摘要:
Allenylstannanes (S)-4 and (R)-4, available in ca. 90% ee from alkynones 1 through reduction with the LiAlH4-Darvon alcohol or -ent-Darvon alcohol complex, followed by S(N)2' displacement on the derived mesylates (R)-3 or (S)-3 with Bu3SnLi.CuBr.Me2S, readily add to various aldehydes under Lewis acid catalysis to afford optically active homopropargylic alcohols with good to excellent syn diastereoselectivity. With 2-(benzyloxy)propanal (48), MgBr2-catalyzed reactions are highly stereoselective, affording the syn adduct 49 from the (S)-stannane (S)-4 and the anti adduct 52 from the (R)-stannane (R)-4. BF3-promoted additions give mainly or exclusively the syn adducts 49 and 51. Additions of (S)- and (R)-4 to (R)-3-(benzyloxy)-2-methylpropanal (61) yield the syn adducts 62 and 64 as major or exclusive products.
Surprising Role of Aryl Halides in Nickel-Catalyzed Reductive Aldol Reactions
作者:Christa C. Chrovian、John Montgomery
DOI:10.1021/ol063028+
日期:2007.2.1
[reaction: see text] A new nickel-catalyzed method for the reductive aldol addition of acrylates and aldehydes has been developed. An unexpected requirement for an aryl iodide additive was found in the process, and the effect was shown to be linked to an initiation step.
Synthesis of enantioenriched homopropargylic alcohols through diastereoselective SE' additions of chiral allenylstannanes to aldehydes
作者:James A. Marshall、Xiao Jun Wang
DOI:10.1021/jo00030a036
日期:1992.2
Allenylstannanes (S)-4 and (R)-4, available in ca. 90% ee from alkynones 1 through reduction with the LiAlH4-Darvon alcohol or -ent-Darvon alcohol complex, followed by S(N)2' displacement on the derived mesylates (R)-3 or (S)-3 with Bu3SnLi.CuBr.Me2S, readily add to various aldehydes under Lewis acid catalysis to afford optically active homopropargylic alcohols with good to excellent syn diastereoselectivity. With 2-(benzyloxy)propanal (48), MgBr2-catalyzed reactions are highly stereoselective, affording the syn adduct 49 from the (S)-stannane (S)-4 and the anti adduct 52 from the (R)-stannane (R)-4. BF3-promoted additions give mainly or exclusively the syn adducts 49 and 51. Additions of (S)- and (R)-4 to (R)-3-(benzyloxy)-2-methylpropanal (61) yield the syn adducts 62 and 64 as major or exclusive products.