Intramolecular nucleophilic acyl substitution reactions of halo-substituted esters and lactones. New applications of organosamarium reagents
摘要:
Intramolecular nucleophilic acyl substitution reactions involving a broad range of halo substituted carboxylic acid derivatives have been accomplished in excellent yield employing samarium(II) iodide as the reductive coupling agent. Although particular substrates cyclized most effectively in THF in the presence of tripiperidinophosphine oxide, carboxylic acid esters, the focus of this report, cyclize equally well without such an additive in the presence of a catalytic quantity of iron(III) complexes. Thus a comprehensive series of halo substituted esters were cyclized in excellent yield to the corresponding 4-, 5-, and 6-membered carbocycles. The reaction is extremely mild and selective as demonstrated by experiments wherein alkyl chlorides, acetals, and olefins remain completely intact under the reaction conditions. In addition to introducing a convenient procedure for preparing stereodefined spirocyclic systems, a new ring expansion sequence has been developed that appears extremely general for the preparation of various ring systems.
A novel selective fragmentation of cycloalkanones by NaNO2/HCl has been established. The C–Cbond cleavage reaction proceeds smoothly under mild conditions, selectively affording versatile keto acids or oxime acids. The methodology can streamline the synthesis of valuable chiral molecules and isocoumarins from readily available feedstocks.
cyclohexanones were synthesized with high regio- and stereoselectivity by allylic substitution followed by ozonolysis. Both alkyl and aryl groups were successfully installed to the cyclohexane ring. The stereochemistry of the SN2′ products was determined to be controlled by the pre-existing chirality on the ring. The present method is highlighted by the synthesis of enantiomerically enriched cyclohexanones
通过烯丙基取代,然后进行臭氧分解,以高区域选择性和立体选择性合成反式-2,6-二取代的环己酮。烷基和芳基均成功安装在环己烷环上。S N 2'产物的立体化学被确定为受环上预先存在的手性控制。通过对映体富集的环己酮的合成突出了本方法。
Organometallic compounds in organic synthesis—part 17
作者:Arthur J. Birch、Lawrence F. Kelly、Acharan S. Narula
DOI:10.1016/0040-4020(82)80256-1
日期:1982.1
Efficient CC bond formation results during reactions of O-silylated enolates and allytrialkysilanes with a range of tricarbonylcyclohexadienyliron salts to give tricarbonylcyclohexadieneiron complexes in good to excellent yields. This represents a new and efficient type of conversion of aldehydes, ketones, esters and lactones, through enol TMS ethers, into synthetically useful products. An advantage
Fluorotetraphenylbismuth: A New Reagent for Efficient Regioselective α-Phenylation of Carbonyl Compounds
作者:Takashi Ooi、Ryoji Goto、Keiji Maruoka
DOI:10.1021/ja030150k
日期:2003.9.1
alpha-alkenylation of carbonyl compounds was also demonstrated by the use of fluoro(2-phenylethenyl)tris(p-tolyl)bismuth (2) as a representative reagent. These results imply the vast potential of organobismuth(V) compounds of type 1 and 2 as useful precursors of a wide variety of pentavalentorganobismuth compounds based on the utilization of the eminent fluorine-silicon interaction or the inherent basicity of the
α-Methylation of Ketones and Indoles Catalyzed by a Manganese(I) PC<sub>NHC</sub>P Pincer Complex with Methanol as a C<sub>1</sub> Source
作者:Ranjeesh Thenarukandiyil、Rohit Kamte、Subhash Garhwal、Philipp Effnert、Natalia Fridman、Graham de Ruiter
DOI:10.1021/acs.organomet.2c00520
日期:2023.1.9
Acceptorless alcohol dehydrogenation is a powerful reaction in sustainable synthesis. When combined in a tandem reaction with dehydrogenative coupling or hydrogenborrowing, acceptorless dehydrogenation can be used for the environmentally benign construction of C–C, C–N, and C–O bonds. While many of these reactions rely on using precious metals, in the past decade the use of earth-abundant metals has