1,3-versus 1,2-Asymmetric induction in the reduction of β-hydroxy ketones by intramolecular hydrosilylation
摘要:
The role of 1,2-asymmetric induction has been investigated in the 1,3-anti-selective reduction of beta-hydroxy ketones via intramolecular hydrosilylation. For the alpha-methyl beta-hydroxy ketones 2a, 3a, the effect of the alpha-substituent is negligible except that it appears to reinforce 1,3-asymmetric induction. For the alpha-ethyl beta-hydroxy ketones 2b, 3b, 1,3-asymmetric induction is dominant but not overwhelming. The super-acid TfOH2+ B(OTf)4- has been used as a catalyst for the hydrosilylation giving, in one case, an improved result when compared with previous methodology.
Directed reduction of .beta.-hydroxy ketones employing tetramethylammonium triacetoxyborohydride
作者:D. A. Evans、K. T. Chapman、E. M. Carreira
DOI:10.1021/ja00219a035
日期:1988.5
The mild reducing agent tetramethylammonium triacetoxyborohydride reduces acyclic P-hydroxy ketones to their corresponding anti diols with high diastereoselectivity. a-Alkyl substitution does not significantly affect the stereoselectivity of these reductions. In all cases examined, good to excellent yields of diastereomerically homogeneous diols were obtained. The mechanism of these reductions involves
温和的还原剂四甲基铵三乙酰氧基硼氢化物以高非对映选择性将无环 P-羟基酮还原为其相应的反二醇。α-烷基取代不会显着影响这些还原的立体选择性。在所有检查的情况下,都获得了良好到极好的非对映异构体均质二醇的产率。这些还原的机制涉及三乙酰氧基硼氢化物阴离子将乙酸盐与底物醇进行酸促进的配体交换。所得氢化物中间体,大概是烷氧基二乙酰氧基硼氢化物,还原近端 OH 0 OH OH 0 Me,NHB(OAc), Mew Me&OR - OR Me he
The directed reduction of β-hydroxy ketones employing Me4NHB(OAc)3
作者:David A. Evans、Kevin T. Chapman
DOI:10.1016/s0040-4039(00)85367-8
日期:1986.1
The diastereoseiective reduction of a range of acyclic β-hydroxy ketones with triacetoxyborohydride is described. In all cases, the anti 1,3-diol diastereomer is the principal product (eq 1).
1,2-anti diastereoselective reduction of 2-alkyl-3-hydroxy-ketones via their silyl ethers
作者:R. Bloch、L. Gilbert、C. Girard
DOI:10.1016/0040-4039(88)85324-3
日期:1988.1
T-butyldimethylsilyl ethers of a range of acyclic 2-alkyl-3-hydroxy-ketones are reduced with lithium aluminum hydride to give with a high 1,2-antidiastereoselective induction syn,anti or anti,anti 2-alkyl-1,3-diols.
Simple Metal Alkoxides as Effective Catalysts for the Hetero-Aldol−Tishchenko Reaction
作者:Cheryl M. Mascarenhas、Matthew O. Duffey、Shih-Yuan Liu、James P. Morken
DOI:10.1021/ol990246c
日期:1999.11.1
[GRAPHICS]This paper reports the utility of simple metal alkoxides for the catalytic, stereoselective hetero-aldol-Tishchenko reaction (eq 1), Choice of metal alkoxide is crucial to achieving high efficiency and stereoselectivity, Whereas NaO-t-Bu is an effective catalyst, delivering one product in 68% yield and 99:1 stereoselection, Sm(O-i-Pr)(3) is less effective and delivers the same product in 42% yield with 4:1 stereoselection.
Tandem Aldol−Tishchenko Reactions of Lithium Enolates: A Highly Stereoselective Method for Diol and Triol Synthesis