Methallyl bromide

Cyclic vinyl ethers have been deprotonated using f-butyllithium in THF (77TL4187). The carbanions formed, which react readily with a variety of electrophiles, constitute a special type of protected acyl anion. Compound (658), available from the metallated pyran (657) and methallyl bromide, gave the /8-vinyl enone (659) on hydrolysis and cyclization (Scheme 152). 

In diethyl ether, the yields of the zinc-mediated Barbier condensation are medium or poor,1 and THF should be preferred for most of the synthetic uses. Sonication is frequently used, e.g. in the reaction of methallyl bromide and salicylaldehyde which provide the expected alcohol27 The condensation of 4-bromo-2-sulfolene with a series of aldehydes and ketones was effected with the zinc-silver couple and ultrasound.28 The reaction occurs without transposition, which is not the case in the presence of magnesium. In refluxing... 

Methallylbenzenc, 353 Methallyl bromide, 354-355 Methally chloride, 305,403 Methanesulfonate esters, 326 Mcthanesulfonic acid, 326 Methanesulfonyl chloride, 326-327 1,6-Methano[10]annulene, 131 Methanolysis, 432433 Methoxyacetyl chloride, 328... 

Preparation. The complex is prepared from 2-methallyl bromide and nickel carbonyl in 85% yield by the method of Semmelhack and Helquist (4, 353). Reaction with carbonyl compounds. The complex reacts with aldehydes and ketones to produce homoallylic alcohols ... 

A few reactions using zinc as the metal in a Barbier process have been published.267 Methallyl bromide and salicylaldehyde sonicated in THF with zinc yield the expected alcohol, which cyclizes by acidic treatment to a chromene.268... 

Related Reagents. Methallyl chloride Methallyl Bromide Methallyl Alcohol 3-Chloro-2-chloromethyl-l-propene 2-Methylene-1,3-propanediol. 

Scheme 8.10 Chemical synthesis of chon-dramide C (Waldmann approach), (a) Benzaldehyde, NaCNBHj, MeOH (b) paraformaldehyde, NaCNBHj, MeOH (52%, two steps) (c) Pd(OH)2, Hj, EtOH-AcOH (d) Fmoc-OSu, NaOH, NajCOj, 1,4-dioxane-HjO, 0°C to r.t. (62%, two steps) (e) LDA, ZnBtj, methallyl bromide, —78°C to r.t. (65%) (f) NaOH (aqueous) (90%) (g) BuLi, (S)-N-benzyl-l-phenylethylamine, —78°C (62%) (h) Pd(OH)2, Hj, EtOH (i) Fmoc-OSu, NaHCOj, l,4-dioxane-H20, 0°C to r.t. (75%, 2 steps) (j) 2-chlorotrityl resin (1.4mmolg ),...

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