Alkynes alkyl halides from

The result of the retrosynthetic analysis of rac-lO is 2-hydroxyphenazine (9) and the terpenoid unit rac-23, which may be linked by ether formation [29]. The rac-23 component can be dissected into the alkyl halide rac-24 and the (E)-vinyl halide 25. A Pd(0)-catalyzed sp -sp coupling reaction is meant to ensure both the reaction of rac-24 and 25 and the ( )-geometry of the C-6, C-7 double bond. Following Negishi, 25 is accessible via carboalumination from alkyne 27, which might be traced back to (E,E)-farnesyl acetone (28). The idea was to produce 9 in accordance with one of the methods reported in the literature, and to obtain rac-24 in a few steps from symmetrical 3-methyl-pentane-1,5-diol (26) by selective functionalization of either of the two hydroxyl groups. 

OxazoIones are alkylated at position 4 by alkyl halides, allyl halides and electrophilic alkynes, such as methyl propiolate (equation 36). In contrast, 2-phenyloxazolones react with methyl vinyl ketone at both C(4) and C(2) to yield a mixture of Michael adducts (equation 37). If the phenyl substituent is replaced by the bulky 2,4,6-trimethylphenyl group the addition is directed exclusively to C(4) (81CB2580). Alkylation of 5(4//)-oxazolones is a key step in the synthesis of ketones from a-amino acids (Scheme 16). The outcome of this sequence is the union of the electrophilic fragment R3 with the group R2CO the amino acid thus functions as the equivalent of an acyl anion (78AG(E)450). 

Alkynes from halides also alkynes from alkynes Esters from alcohols also esters from carboxylic acids Alkyls from alkenes (Conjugate Reduction)... 

Terminal alkynes are weakly acidic. The alkyne hydrogen can he removed by s strong base 9uch ae Na NH.. to yield nn a<%tylide anipn An acetylide anion ads as a nucleophile and can displace a halide ion from a primary alkyl halide in a n alkylation reaction. Acetylide anions are more stable iJian either alkyl anions or vinylic anions because their m ative charge is in a hybrid orbital with 50% s character, allowing the charge to be doser to the nucleus. 

The substitution reactions of alkyl halides by carbon nucleophiles derived from alkynes and enolate anions provide major methods for the... 

From Aryl halide Alkyl, vinyl halide Alkene. Alkyne... 

Acylcobalt tetracarbonyl complexes, formed from Na[Co(CO)4] and alkyl or acyl halides, react with alkynes to give 2,4-pentadieno-4-lactones (Scheme 20). The reaction is catalytic in cobalt and yields are around 60% for a variety of substituted alkynes and alkyl halides. 

Since sodium methyl acetylide is the salt of the extremely weak acid, methyl acetylene, the acetylide ion is a stronger base, thus this reaction involves substitution of acetylide ion for halide ion. From this it can readily be seen that the metal ion, sodium, bonds to the released halide ion and the acetylide ion bonds to the alkyl group yielding a higher alkyne, plus a metal halide as the byproduct. 

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