Diastereo- and Enantioselective Synthesis of (E)-2-Methyl-1,2-syn- and (E)-2-Methyl-1,2-anti-3-pentenediols via Allenylboronate Kinetic Resolution with (dIpc)2BH and Aldehyde Allylboration
摘要:
Enantioselective hydroboration of racemic allenylboronate (+/-)-1 with 0.48 equiv of ((d)Ipc)(2)BH at -25 degrees C proceeds with efficient kinetic resolution and provides allylborane (R)-Z-4. When heated to 95 degrees C, allylborane (R)-Z-4 isomerizes to the thermodynamically more stable allylborane isomer (S)-E-7. Subsequent allylboration of aldehydes with (R)-Z-4 or (S)-E-7 at -78 degrees C followed by oxidative workup provides 1,2-syn- or 1,2-anti-diols, 2 or 3, respectively, in 87-94% ee.
Efficient Organocatalytic Cross-Aldol Reaction between Aliphatic Aldehydes through Their Functional Differentiation
作者:Taichi Kano、Hisashi Sugimoto、Keiji Maruoka
DOI:10.1021/ja208873k
日期:2011.11.16
stereoselective asymmetric directcross-aldolreactionbetween aliphatic aldehydes and α-chloroaldehydes has been developed as a method for the formation of the sole cross-aldol adduct with both enantio- and diastereocontrol, and either anti- or syn-aldol adducts were obtained in good to excellent stereoselectivities by use of proline or a novel axiallychiralaminosulfonamide as catalyst.
Regioselective Alkyl and Alkynyl Substitution Reactions of Epoxy Alcohols by the Use of Organoaluminum Ate Complexes: Regiochemical Reversal of Nucleophilic Substitution Reactions
作者:Minoru Sasaki、Keiji Tanino、Masaaki Miyashita
DOI:10.1021/ol010062+
日期:2001.5.1
Unprecedented nucleophilic substitution reactions of 2,3-epoxy-1-alkanols with alkyl and alkynylaluminum ate complexes have been studied and demonstrated to occur at the C2 position with extremely high stereoselectivity, i.e., with exactly reversed regioselectivity to that obtained in the substitution reactions by normal organoaluminum reagents, resulting in the formation of the C2-alkyl and C2-alkynyl substitution products in excellent yields.
Nakata, Tadashi; Tani, Yoichiro; Hatozaki, Masayoshi, Chemical and pharmaceutical bulletin, 1984, vol. 32, # 4, p. 1411 - 1415
Diastereo- and Enantioselective Synthesis of (<i>E</i>)-2-Methyl-1,2-<i>syn</i>- and (<i>E</i>)-2-Methyl-1,2-<i>anti</i>-3-pentenediols via Allenylboronate Kinetic Resolution with (<sup><i>d</i></sup>Ipc)<sub>2</sub>BH and Aldehyde Allylboration
作者:Jeng-Liang Han、Ming Chen、William R. Roush
DOI:10.1021/ol3010968
日期:2012.6.15
Enantioselective hydroboration of racemic allenylboronate (+/-)-1 with 0.48 equiv of ((d)Ipc)(2)BH at -25 degrees C proceeds with efficient kinetic resolution and provides allylborane (R)-Z-4. When heated to 95 degrees C, allylborane (R)-Z-4 isomerizes to the thermodynamically more stable allylborane isomer (S)-E-7. Subsequent allylboration of aldehydes with (R)-Z-4 or (S)-E-7 at -78 degrees C followed by oxidative workup provides 1,2-syn- or 1,2-anti-diols, 2 or 3, respectively, in 87-94% ee.