Carbonates, allylic, coupling compounds

The second dynamic process involves C—Li exchange. Around and below 230 K, most of the internally solvated allylic lithium compounds exhibit one bond spin coupling between 13C and 7Li (/ = 3/2) and to 6Li (/ = 1). The 13C NMR of lithium bound carbon consists of equally spaced equal multiplets, an equal triplet for coupling to 6Li and an equal quartet for coupling to 7Li. The separation between adjacent lines are the coupling constants. 

The palladium-catalysed coupling of allylic esters with carbanions has now been extended to include other reactions. The allylic carbonate 299 couples with the nitro compound 300 to give the expected product 301 in good yield. 

Jiuc couplings have been observed by Fraenkel et al in four allylic lithium compounds prepared with a tethered ligand, (CH30CH2CH2)2 NCH2C(CH3)2-L, attached to a terminal allyl carbon. These were equimolar equilibrium mixtures of 3-enrfo-L-allyllitium with 3-exu-L-allyllitium, and l-evo-TMS-3-e do-L-allyllitium with l-exo-TMS-3-exu-L-allyllitium where Jciu of 5.2, 9.1, 3.5 and 6.8 Hz, respectively, have been observed for C-1 the couplings between the lithium and C-2 nuclei were considerably smaller, of ca. 2 Hz or less. 

The Pd-catalyzed cross-coupling reactions of metal nucleophiles with carbon electrophiles are of considerable value for the regio- and stereocontrolled synthesis of functionalized organometallic compounds, in particular, silanes, stannanes, and boianes, which are important reagents for Pd-catalyzed carbon-carbon CTOss-coupling as shown in Sects. III.2.2-in.2.4. Symmetrical bimetallic compounds such as disilanes, distannanes, and diborons are usually used as metal nucleophiles. The present metallation is applicable to aryl, benzyl, vinyl, acyl, and allyl (Sect. V.2.3.3) electrophiles. 

Dienes and allylarcncs can be prepared by the Pd-catalyzcd coupling of allylic compounds with hard carbon nucleophiles derived from alkenyl and aryl compounds of main group metals. Allylic compounds with various leaving groups can be used. Some of them are unreactive with soft nucleophiles, but... 

Another example of a [2s+2sh-1c+1co] cycloaddition reaction was observed by Barluenga et al. in the sequential coupling reaction of a Fischer carbene complex, a ketone enolate and allylmagnesium bromide [120]. This reaction produces cyclopentanol derivatives in a [2S+2SH-1C] cycloaddition process when -substituted lithium enolates are used (see Sect. 3.1). However, the analogous reaction with /J-unsubstituted lithium enolates leads to the diastereoselective synthesis of 1,3,3,5-tetrasubstituted cyclohexane- 1,4-diols. The ring skeleton of these compounds combines the carbene ligand, the enolate framework, two carbons of the allyl unit and a carbonyl ligand. Overall, the process can be considered as a for-... 

Allyl silanes react with epoxides, in the presence of Bp3-OEt2 to give 2-allyl alcohols. The reaction of a-bromo lactones and CH2=CHCH2Si SiMe3)3 and AIBN leads to the a-allyl lactone. " Benzyl silanes coupled with allyl silanes to give ArCH2—R derivatives in the presence of VO(OEt)Cl2 " and allyltin compounds couple with allyl silanes in the presence of SnCU. " Allyl silanes couple to the a-carbon of amines under photolysis conditions. ... 

In 1981, it was demonstrated (70) that anions of nitro compounds can be involved in C,C-coupling with allyl acetates at the allylic carbon atom with the use of metal complex catalysis. For many years, this observation did not come to the attention of chemists interested in the synthesis of cyclic nitronates. However, Trost demonstrated (71) that this process can be used in the synthesis of five-membered cyclic nitronates from olefins (18) containing two acyl groups in the different allylic positions (Scheme 3.21). 

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