Synthesis of Both Antipodal Forms of 7,7-Dimethylbicyclo[2.2.2]oct-2-en-5-one by Enantiomer Interconversion
摘要:
An enantioselective synthesis of both enantiomers of the title ketone 5 from a common achiral beta-diketone is reported. Bakers' yeast reduction of 6 cleanly differentiates between the two carbonyl groups to deliver (+)-9 in >90% yield, and with an ee exceeding 98%. Direct xanthate elimination leads to (+)-5. To arrive at the levorotatory antipode, the OH group in the beta-hydroxy ketone is transformed into the tetrahydropyranyl ether and the carbonyl group is subsequently reduced in advance of formal dehydration. Oxiadtion of the deprotected alcohol ultimately reestablishes the carbonyl functionality and delivers (-)-5 of equally high optical purity.
Efficient Addition of Allylsilanes to α,β-Enones Using Catalytic Indium and Trimethylsilyl Chloride
作者:Phil Ho Lee、Dong Seomoon、Sundae Kim、K. Nagaiah、S. V. Damle、Kooyeon Lee
DOI:10.1055/s-2003-41017
日期:——
β-Enones undergo an efficient Hosomi-Sakurai reaction with allyltrimethylsilane, in which a catalytic amount of indium is used in the presence of trimethylsilylchloride as an activator under mild conditions to produce the conjugateaddition products in good yields.
A flexible, unified radical-based approach to polycyclic structures
作者:Rama Heng、Samir Z. Zard
DOI:10.1039/c1ob00024a
日期:——
Cis- and trans-decalins, trans-perhydroazulenes, and [5.3.1]-bicyclo-undecanone scaffolds can be readily constructed starting from unsaturated ketones and using the degenerative xanthate transfer technology to accomplish unusual and otherwise difficult radical cyclisations.
Forskolin: some stodies on ring B forming reactions
作者:Dirk Neunert、Harald Klein、Peter Welzel
DOI:10.1016/0040-4020(89)80095-x
日期:1989.1
Cyclization of the unsaturated sulfoxides 18b,18c underPummererconditions provided the six-membered products 20a and 21a, whereas base-catalyzed cyclization of the stereoisomeric epoxysulfones 16a,16b and 17a,17b led exclusively to the five-membered compounds 12a,12b and 15a,15b. The reaction 18b,18c → 20a,21a has been used to prepare the trans-decaline derivative 24 starting from the dimethylcyclohexenone
Bistrifluoromethanesulfonimide may be used directly to initiate the catalytic conjugate allylation of alpha,beta-unsaturated carbonyl compounds with allyltrimethylsilane; high yields of either silyl enol ethers or delta,epsilon-unsaturated ketones and esters may be obtained under mild conditions. (C) 1998 Elsevier Science Ltd. All rights reserved.