Acid chlorides, reaction with alkyne anions

Now, let s draw out the forward scheme. This multi-step synthesis uses three equivalents of ethylene (labeled A, B, C in the scheme below) and one equivalent of acetic acid (labeled D). Ethylene (A) is converted to 1,2-dibromoethane upon treatment with bromine. Subsequent reaction with excess sodium amide produces an acetylide anion which is then treated with bromoethane [made tfom ethylene (B) and HBr] to produce 1-butyne. Deprotonation with sodium amide, followed by reaction with an epoxide [prepared by epoxidation of ethylene (C)] and water workup, produces a compound with an alkyne group and an alcohol group. Reduction of the alkyne to the cis alkene is accomplished with H2 and Lindlar s catalyst, after which the alcohol is converted to a tosylate with tosyl chloride. Reaction with the conjugate base of acetic acid [produced by treating acetic acid (D) with NaOH] allows for an Sn2 reaction, thus yielding the desired product, Z-hexenyl acetate. 

Benzonitrile oxide (C in Figure 15.44) is an isolable 1,3-dipole. It can be generated from benzaldoxime and anNaOH/Cl2 solution. Under these reaction conditions the oxime/nitroso anion (A B) is initially formed and chlorine disproportionates into Cl—O and chloride. An SN reaction of the negatively charged C atom of the anion A B at the Cl atom of Cl— O or of Cl—O—H affords the oc-chlorinated nitroso compound E, which tautomerizes to the hydroxamic acid chloride D. From that species, the nitrile oxide C is generated via a base mediated 1,3-elimination. Isoxazoles are formed in the reactions of C with alkynes (Figure 15.44), while isoxazolines would be formed in its reactions with alkenes. 

Jacobi s synthesis of ( )-paniculide-A involves an intramolecular Diels-Alder reaction of the alkynic ketone (31). This compound was prepared in >90% yield (Scheme 9) by acylation of a lithium alkynide with the A7-methoxy-A7-methylamide (30). Addition of the anion to other derivatives related to (30) such as an acid chloride, a trifluoroacetic mixed anhydride, an acyl imidazole, S-(2-pyridyl) thiolates and a mixed carbonic anhydride (from ethyl chloroformate) led to either bis-addition or to proton abstraction. Notice should be made of the stability exhibited by the A7-methoxy-A7-methylamide group while the oxa-zole moiety was being introduced. ... 

A new synthesis of aldehydes with 2-methyl-2-thiazoline has the advantage of releasing the aldehydes from the thiazolidine intermediate under neutral conditions . Acetylene derivatives can be obtained from aldehydes via dibromomethylene compounds Novel reactions of alkynes with cationoid electrophiles have been published. -Diketones and 2-ketoalkoximes can be obtained by this reaction from acid chlorides and aliphatic nitro compounds respectively Addition of aldehydes to activated carbon-carbon double bonds occurs smoothly in the presence of cyanide ions as catalysts . Poly- -carbonyl compounds have been prepared by condensation of two anions, whereby the enolate salt of a y8-keto ester condenses as an electrophilic anion with strong nucleophiles such as the dianion of benzoylacetone. ... 

---