Allyl bonded

Fluorides and 0x0 compounds of Ru and Os have already been mentioned, and salts such as (R4N)[Ru04l, (R = n-propyl, n-butyl) are useful reagents to oxidize a variety of organic materials without attacking double or allylic bonds,... 

Chain propogation is by hydrogen abstraction by rominc radicals. The weakest C-H bond is broken, that the allylic bond, to give the most stable radical (2)... 

Allyl carbonate esters are also useful hydroxy-protecting groups and are introduced using allyl chloroformate. A number of Pd-based catalysts for allylic deprotection have been developed.209 They are based on a catalytic cycle in which Pd° reacts by oxidative addition and activates the allylic bond to nucleophilic substitution. Various nucleophiles are effective, including dimedone,210 pentane-2,4-dione,211 and amines.212... 

The N-allyl bond was hydrogenolyzed by heating the N-protected compound in a nitrobenzene-p-xylene mixture (1 1) in the presence of a catalytic amount of 10% Pd/C and molecular sieves (Scheme 4.107).355 356... 

The rupture of an allylic bond, followed by an energetically favoured hydrogen migration, leads to the linear, ionized conjugated triene (14). The molecular ion of triene 14 is comparable to the compound 7 molecular ion7. 

It is useful to consider the possible formulations of alkyne and allyl bonding to metals in terms of Green s MLX formalism.64 Coordination of an alkyne in a simple dative two-electron fashion is denoted ML, whereas the limit of metallacyclobutene formation is denoted MX2. For the allyl ligand, three imaginable coordinations are possible simple q1 coordination is denoted MX, butq3 coordination can encompass both MLX (one a bond plus a dative alkene coordination) and MX3 (three M—C a bonds). 

The Sn-allyl bond (but not Sn-alkyl, Sn-vinyl, Sn-benzyl, or Sn-aryl) reacts with C02 in the presence of a palladium catalyst to give a tin buteneoate. A mechanism can be envisaged which involves the formation of the Sn-Pd-allyl structure, which undergoes C02 insertion to give Sn-Pd-OCO-allyl, followed by reductive elimination of the tin carboxylate (Equation (131)).345... 

The cationic complex [Ni(bpy)3](BF4)2 is a good catalyst for the electroreductive cleavage of the C—O (allyl) bond of allyl ethers, affording parent alcohols or phenols. The Ni(II)-catalyzed electroreductive deprotection of allyl ethers is found to proceed in a DMF-Bu4NBp4-(Mg) system. For... 

Figure 8. 5is-allylic carbon-hydrogen bond. The dissociation energy of this bond is lower than allylic and alky] carbon-hydrogen bonds, and therefore the iiy-allylic bond is favored for attack by LOO which explains the susceptibility of polyunsaturated lipids. 

As far as we are aware, these observations are the first that show that the well-known Norrish Type I reactions of p,7-unsaturated carbonyl compounds can take place by excitation of the alkene moiety rather than the carbonyl group. This unusual reactivity may be due to the fact that the TiC-ir, -ir ) excited states of 53 and 55 possess sufficient energy to promote the homolytic allylic bond fission to form the stabilized pentadienyl radical 57. As a result, photodecarbony-lation competes favorably with the ODPM rearrangement. 

Allylthiobenzimidazole 176 reacted with sulfur monochloride to give trithiazepinobenzimidazole 178 (2002MI317). The formation of intermediate 177 by S2CI2 addition to the double allylic bond was proposed (Scheme 90). 

An NOE study of the intermediate [Pd(ti -PhCHCHCHPh)(Binap)], 82, thought to be involved in the Pd-catalyzed allylic alkylation of a 1,3-diphenylpropene, revealed that two phenyl rings, one from the auxiliary, D, and one from the substrate, F, are forced to take up parallel positions, i.e, they are 7i-stacked, as shown in 83 [103]. Since the ti-stacking is repulsive, and thus selectively weakens one of the two Pd-C(allyl) bonds, the reaction becomes stereoselective. The D and F rings do not show inter-ligand NOEs. 

The mass spectrum of /3-myrcene, a terpene, is shown in Figure 2.7. The peaks at m/z 41, 55, and 69 correspond to the formula CnH2n x with n = 3, 4, and 5, respectively. Formation of the m/z 41 peak must involve rearrangement. The peaks at m/z 67 and 69 are the fragments from cleavage of a bi-allylic bond. 

Insertion involves a transitory a-allyl-bonded chain and -coordinated monomer eventually leading to the re-formation of the rr-allyl chain complex.380-382... 

The rearrangement of / ,y-unsaturated ketones can be viewed formally as the result of a preferential a-cleavage of the allylic bond to the resulting resonance-stabilized allyl radical with a widened range of recombination pos-[ sibilities. Thus ketone (16) photorearranges in /-butanol to the cyclopropyl... 

---