5-Allyl-derivatives from 5-bromo compounds

While treatment in HBr + AcOH by the Tarbell method424 leads directly from allylphenols 168 to compounds 169, other methods involve the formation of the brominated derivative obtained by adding HBr (in the presence of diphenylamine) to the allylphenol.432 Ring closure is effected by sodium ethoxide. Thus, the ll//-furo[3,2-a]xanthone derivative (177) can be obtained either directly from the allyl derivative (175) or via the bromo derivative (176).432 433 Similarly, 179 has been obtained from the chromone 178.434... 

Tetrahedrane (11) is the ruthenium analog of the much-studied tricobaltnonacarbonyl clusters Co3(CO)9CR see Cobalt Organometallic Chemistty). The substitution chemistry of (11) has been studied. A starting material is prepared from (11) by reaction with BX3 (equation 2), which gives the chloro and bromo compounds (12). In addition, (11) can also be treated directly with compounds such as diynes to yield interesting substitution products. For example, when (11) is refluxed in THF with diphenylbutadiyne, cis- and trans-alkene isomers of two alkyne insertion regioisomers are formed (equation 3). The product seems to arise from dehydrogenation of one end of the diyne to yield cis and trans enynes and an imsaturated monohydride cluster intermediate, which then reacts with the enynes to yield the allylic derivative products... 

Dilithium tetrachlorocuprate is recommended as an additive for cross coupling of Grignard compounds with tosylates even allylic and benzylic acetates give good yields . a-Methylene-ketones, -carboxylic acids and -lactones have been prepared via sulfides and sulfoxides. A convenient and general synthesis of acetylene derivatives from boranes via the reaction of iodine with lithium 1-alkynyltriorganoborates has been published ar-Nitrostyrenes can be easily obtained by a Wittig synthesis with formaldehyde in an aqueous medium . A new synthesis of unsym. ketones by reaction of dialkyldiloroboranes with lithium aldimines has recently been published . Metallo aldimines have also served for the synthesis of a variety of other compound classes such as a-hydroxyketones, a-keto acids, nitriles, and for the asym. synthesis of a-amino acids . Polycondensations of malononitriles with benzylic chlorides have been carried out quantitatively under mild conditions in dimethyl sulfoxide with triethylamine as acid acceptor . Carbonyl compounds can react with dibromoacetonitrile to yield a-bromo esters with additional carbon atom . ... 

In both these experiments, as with other conjugated radicals (e.g. benzyl), high yields of radicals can be obtained from the chloro-deriva-tives, whereas for saturated radicals the yield is markedly reduced if the chloro-derivatives are used instead of the bromo- or iodo-compounds. This reflects the reduced bond strengths of the allylic group adjacent to the double bond. For example D C—Cl) = 82 kcal mole in CH3.CH2.CH2CI (Benson and Bose, 1963), whereas H(C—Cl) = 60 kcal mole in CHg CH. CH.2CI (Lossing et al., 1954). 

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.On the other hand, silyl epoxides have been prepared from epoxides via reaction with iec-butyllithium and chlorotri-methylsilane. ° a-Silyl-A-Boc-amines were prepared in a similar manner from the A-Boc-amine. " Arylsilanes were prepared by reaction of an aryl-lithium intermediate with TfOSi(OEt)3. In the presence of BEs etherate, allyl silane and a-methoxy A-Cbz amines were coupled. Benzyl silanes coupled with allyl silanes to give ArCHa—R derivatives in the presence of VO(OEt)Cl2 " and allyltin compounds couple with allyl silanes in the presence of SnCl4. Allyl silanes couple to the a-carbon of amines under photolysis conditions. 

A -Boc amines are made from the metallated /-hutyl Af-tosyloxycarbamate. Allylic displacements. Applications of this process include vinyl- and allyltin compounds. Homoallylic alcohols asymmetrically substituted at the allylic position are obtained from 4-bromo-2-alkenoyl derivatives of camphor sultam in two... 

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