Chlorides, tertiary allylic

Reduction of halides.1 The reagent prepared from NaBH3CN and SnCl2 in a 2 1 ratio does not reduce primary or secondary alkyl halides or aryl halides in ether at 25°, but does reduce tertiary, allyl, and benzyl halides. It is thus comparable to NaBH3CN-ZnCl2 (12, 446). Aldehydes, ketones, and acid chlorides are reduced to alcohols, but esters and amides are inert. 

The tertiary allylic chlorides labeled above with an asterisk are the grafting sites (1). Tetrahydrofuran (THF) was chosen as the heterocyclic monomer because its chemistry is so well known that it is the model heterocycle of choice in oxonium-ion polymerizations (2). 

The transformation of an allylic alcohol to an allylic halide (equation 5) or the reverse reaction normally leads to a mixture of isomers of direct and allylic substitution products. Only when tertiary allylic alcohols are employed or a rearrangement leads to extended conjugation of double bonds does a transposition of functionality occur predominantly While a number of procedures have been developed for the conversion of allylic alcohols to halides without rearrangement, there seems to be only one reaction where a cleanly rearranged product is obtainable in a substitution of a primary or secondary allylic (and propargylic) hydroxy group to a chloride, that is by thionyl chloride in ether, probably by a cyclic SNi process. The regioselectivity is worse in other solvents and is lost in the presence of a base. In accordance with the mechanism it is a syn facial substitution, as has been demonstrated in cyclic cases (equa-... 

These chlorine atoms were activated by addition of AgPF6 (in excess over the tertiary allylic chlorides) in the presence of THF this monomer was quantitatively grafted from the neoprene backbone ... 

P-Ketoesters are oxidized at the a-position with oxygen in the presence of either manganese(II) acetate " or cobalt(II) chloride." Cyclic allyl phosphonates give y-acetoxy a,p-unsaturated phosphonates when they are exposed to oxygen in HOAc containing PdCl2 and isopentyl nitrite. " Tertiary amine oxides are formed under cooxidation conditions, that is, O2, Fe203, and isovaleraldehyde. "... 

SOLUTION TO 11a First we need to determine which of the terminal sp carbons of the conjugated system is going to be the C-1 carbon. The proton will be more apt to add to the indicated sp carbon because the carbocation that is formed shares its positive charge with a tertiary allylic and a secondary allylic carbon. If the proton were to add to the sp carbon at the other end of the conjugated system, the carbocation that would be formed would be less stable because its positive charge would be shared by a primary allylic and a secondary allylic carbon. Therefore, 3-chloro-3-methylcyclohexene is the 1,2-addition product and 3-chloro-l-methylcyclohexene is the 1,4-addition product. 3-Chloro-3-methylcyclohexene is the kinetic product because of the chloride ion s proximity to C-2, and 3-chloro-l-methylcyclohexene is the thermodynamic product because its more highly substituted double bond makes it more stable. 

Reaction with allylic ethers. Alkenes are obtained by reaction of allylic ethers with Grignard reagents catalyzed by cuprous chloride or bromide. Direct replacement of the ether group takes place as the major reaction when the ether is primary. Secondary and tertiary allylic ethers react mainly with rearrangement. 

All these developed living cationic polymerization methods for isobutene provide defined tertiary chloride end groups, opening up possibilities for further end-group functionalization. A representative example was reported by Ivan and Kennedy, who described the quantitative conversion of the chloride into allyl-terminated PIB, which was converted into epoxy and hydroxyl-functional PIBs [34]. 

Rates Allylic halides are more reactive in S l processes than nonallylic halides. For example, the tertiary allylic chloride shown undergoes solvolysis in ethanol over 100 times faster than tert-huiy chloride. 

Z or to tail E- or tertiary allylic isomerized primary trans (inverted) cis chloride allylic chloride 3,4-Addition... 

Tertiary, allyl, and benzyl alcohols react to give an immediate cloudiness to the solution. You may be able to see a separate layer of the alkyl chloride after a short time. 

Trivinyl aluminium (AlVy,) has been employed as a cationic initiator for the preparation of ,co-dienepolyisobutylene. It also functions as a vinylating agent for tertiary alkyl, and secondary and tertiary allyl chlorides, and has been used, as in Scheme 10, for vinylating chlorinated ethylene-propylene rubber. ... 

Subsequently, this version of Claisen rearrangement was extended to tertiary allyl amines and acyl chlorides [87], Using Lewis acid catalyst, excellent stereoselectivity of the product was found. For example, 3,3-disubstituted aUyl morpholine 125 with propionyl chloride in the presence of TiCLt gives highly stereoselective syn product 126 [87]. This method is useful for the synthesis of... 

Relative Sf l Rates Under SnI conditions such as solvolysis in ethanol, the tertiary allylic chloride 3-chloro-3-methyl-l-butene reacts over 100 times faster than tert-butyl chloride. Both reactions follow a first-order rate law, and their relative rates reflect the greater stability of [(CH3)2C=CH=CH2] compared with (CHjjjC. ... 

Polychloroprenes differ from other polydienes in that conventional sulphur vulcanization is not very effective. The double bonds are deactivated by the electronegative chlorine atoms and direct reaction with sulphur is limited. The vulcanization of polychloroprenes is normally achieved by heating at about 150°C with a mixture of zinc and magnesium oxides W type neoprenes also require an organic accelerator (commonly either a diamine or ethylene thiourea) but G types cure quite rapidly without acceleration. The mode of reaction has not been established with certainty, but it is generally supposed that cross-linking occurs at the tertiary allylic chloride structures generated by 1,2-polymerization (see section 20.8.3) and that a 1,3-allylic shift is the first step. The metal oxides may lead to ether cross-links as follows ... 

After it was demonstrated by the contributions of several research groups that the hard enolates of ketones are susceptible to the palladium-catalyzed allylic alkylation, it was an obvious idea to investigate amide enolates next, as they are equally stable. Thus, Hou and coworkers reported that the lithium enolates of tertiary amides 32 undergo in the presence of hthium chloride enantioselective allylic alkylation with allyl or methallyl acetate 33. The reaction was mediated by the ferrocene-based ligand 34, and the enantiomeric excess of the products 35 was found to range from 73 to 93% ee. The absolute configuration was determined in two cases (for = Me, Et, = H) to be R) (Scheme 5.12) [21]. An allylation... 

A substantial body of evidence indicates that allylic carbocations are more stable than simple alkyl cations For example the rate of solvolysis of a chlonde that is both tertiary and allylic is much faster than that of a typical tertiary alkyl chloride... 

---