F Allyl formate

Allyl benzenesulfonate, 3149 f Allyl formate, 1521 Allyl hydroperoxide, 1222... 

Allyldimethylarsine, 1983 f Allyl ethyl ether, 1955 f Allyl formate, 1524... 

A. 1.1. Covalently Functionalized Dendrimers Applied in a CFMR The palladium-catalyzed allylic substitution reaction has been investigated extensively in the preceding decades and provides an important tool for the formation of carbon—carbon and carbon—heteroatom bonds 14). The product is formed after attack of a nucleophile to an (f/ -allyl)Pd(II) species, formed by oxidative addition of the unsaturated substrate to palladium(0) (Scheme 1). To date several nucleophiles have been used, mostly resulting in the formation of carbon—carbon and... 

Propenyl hydroperoxide, see Allyl hydroperoxide, 1222 f 3-Propenyl methanoate, see Allyl formate, 1521... 

For a long time it was believed that the trifluorovinyl group is not basic enough to stabilize an a-carbocationic center, and perfluorinated allylic cations were thought not to be stable [15,21,59]. However, in 1984 the formation of the F-methallyl cation 30 in the reaction of PFIB with SbF5 in S02C1F solvent was reported [74], followed by the F-allyl cation (1) [75] ... 

The mechanism includes formation of F-allyl carbocation 1 as a result of abstraction of activated allylic fluorine from HFP by a Lewis acid and addition 1 to TFE followed by isomerization of terminal olefin into product 11 ... 

Scheme 3 Reagents, (a) Allyl bromide/Acetone followed by optical resolution (b) Benzyl chloroformate, NaHC03 (aq), CHC13(98%) (c) Pd/C, H20, AcOH (100%) (d) di-tert-butyl dicarbonate, CH2C12 (98%) (e) Pd/C, Ammonium formate, MeOH (97%) (f) Allyl bromide, K2CQ3, Acetone (98%) (g) TFA, Triethylsilane, CH2C12(89%) (h) Pd/C, H2Q, AcOH [60]...

The reactions of Pd " with cyclopropanes lead to skeletal rearrangements and appear to be initiated by the heterolytic cleavage of the most substituted C—C cyclopropane moiety (equation 13). Two cleavage modes were observed which lead in the primary step to the formation of tertiary carbocations followed by successive deprotonation to the f/ -allyl complex 31 as the major pathway. 

On the other hand, an enantioselective fluorination of allylic alcohols (256) has been achieved using phosphoric acid bearing 1-adamantyl and 2,6-diisopropyl substituents attached to a BINOL scaffold (257) (Scheme 68). Mechanistic studies suggested that this transformation proceeded through a concerted enantiodetermining transition state involving both C-F bond formation and C-H bond cleavage. ... 

The allylic position of olefins is subject to attack by free radicals with the consequent formation of stable allylic free radicals. This fact is utilized in many substitution reactions at the allylic position (cf. Chapter 6, Section III). The procedure given here employs f-butyl perbenzoate, which reacts with cuprous ion to liberate /-butoxy radical, the chain reaction initiator. The outcome of the reaction, which has general applicability, is the introduction of a benzoyloxy group in the allylic position. 

Now that the allylic oxidation problem has been solved adequately, the next task includes the introduction of the epoxide at C-l and C-2. When a solution of 31 and pyridinium para-tolu-enesulfonate in chlorobenzene is heated to 135°C, the anomeric methoxy group at C-l 1 is eliminated to give intermediate 9 in 80% yield. After some careful experimentation, it was found that epoxy ketone 7 forms smoothly when enone 9 is treated with triphenyl-methyl hydroperoxide and benzyltrimethylammonium isopropoxide (see Scheme 4). In this reaction, the bulky oxidant adds across the more accessible convex face of the carbon framework defined by rings A, E, and F, and leads to the formation of 7 as the only stereoisomer in a yield of 72%. 

Scheme 35 Sequential formation of rings I and H by intramolecular allylation/RCM in Yamamoto s synthesis of the F-K ring segment 186 of brevetoxin B (184) [91]...

Complex a is readily converted into a Fe-y-H agnostic complex b within an early picosecond timescale and then the 7i-allyl hydride complex c is generated by hydride abstraction. The energy level of the 2-alkene isomer d, which is calculated by DPT experiments, is similar to that of the 1-alkene complex b. In the next step, Fe (CO)3(t -l-alkene)(ri -2-alkene) f, which is generated via intramolecular isomerization of the coordinated 1-alkene to 2-alkene and the coordination of another 1-alkene, is a thermodynamically favored product rather than formation of a Fe(CO)3(ri -l-alkene)2 e. Subsequently, release of the 2-aIkene from f regenerates the active species b to complete the catalytic cycle. 

A possible reaction mechanism shown in Scheme 7-10 includes (a) oxidative addition of the S-H bond to Pd(0), (b) insertion of the allene into the Pd-H bond to form the tt-allyl palladium 38, (c) reductive elimination of allyl sulfide, (d) oxidative addition of the I-aryl bond into the Pd(0), (e) insertion of CO into the Pd-C bond, (f) insertion of the tethered C=C into the Pd-C(O) bond, and (g) P-elimination to form 37 followed by the formation of [baseHjI and Pd(0). 

The silyl ketene acetal rearrangement can also be carried out by reaction of the ester with a silyl triflate and tertiary amine, without formation of the ester enolate. Optimum results are obtained with bulky silyl triflates and amines, e.g., f-butyldimethylsilyl triflate and (V-methyl-Af, /V-dicyclohcxylaminc. Under these conditions the reaction is stereoselective for the Z-silyl ketene acetal and the stereochemistry of the allylic double bond determines the syn or anti configuration of the product.243... 

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