Acetylide ions acylation

Other carbanionic groups, such as acetylide ions, and ions derived from a-methylpyridines have also been used as nucleophiles. A particularly useful nucleophile is the methylsulfinyl carbanion (CH3SOCHJ), the conjugate base of DMSO, since the P-keto sulfoxide produced can easily be reduced to a methyl ketone (p. 549). The methylsulfonyl carbanion (CH3SO2CH2 ), the conjugate base of dimethyl sulfone, behaves similarly, and the product can be similarly reduced. Certain carboxylic esters, acyl halides, and DMF acylate 1,3-dithianes (see 10-10. )2008 Qxj(jatjye hydrolysis with NBS or NCS, a-keto aldehydes or a-... 

Again we need a reagent for an acyl anion synthon (A). Ve find this in the acetylide ion since substituted acetylenes can be hydrated to ketones ... 

Specific enol equivalents (e. g. (3-keto esters) and umpolung (e. g., with cyanide or acetylide ions as acyl anion equivalents) have of course been used in synthesis for many years. What is new is the recognition of their role, as a result of the disconnec-... 

All three target molecules in this problem have more than six carbons, so all answers will include carbon-carbon-bond-forming reactions. So far, there are three types of reactions that form carbon-carbon bonds the Grignard reaction, S 2 substitution by an acetylide ion, and the Friedel-Crafts reactions (alkylation and acylation) on benzene. 

Disconnection of a-hydroxy ketones such as (4) requires acyl anion (5) equivalents. We have already met two of these, the nitro compounds in the last chapter and the acetylenes in Chapter 16. The acetylide ion is satisfaaory here, adduct (6) being hydrated to TM(4) with Hg(II) catalysis. 

The usual a.d-disconnection on (47) is not very productive as it suggests a 1,7-dicarbonyl precursor (49), but the strategically preferable ring-chain disconnection is good providing we have a reagent for acyl anion (SO). We have already met the synthesis of (47) using acetylide ion as the acyl anion equivalent (Chapter 16). 

DNA sequencing and. 1113 Electrospray ionization (ESI) mass spectrometry, 417-418 Electrostatic potential map, 37 acetaldehyde, 688 acetamide, 791,922 acetate ion. 43. 53, 56, 757 acetic acid. 53. 55 acetic acid dimer, 755 acetic anhydride, 791 acetone, 55, 56. 78 acetone anion, 56 acetyl azide, 830 acetyl chloride, 791 acetylene. 262 acetylide anion, 271 acid anhydride, 791 acid chloride, 791 acyl cation, 558 adenine, 1104 alanine, 1017 alanine zwitterion, 1017 alcohol. 75 alkene, 74, 147 alkyl halide, 75 alkyne. 74... 

Fluonnated ylides have also been prepared in such a way that fluorine is incorporated at the carbon p to the carbamomc carbon Various fluoroalkyl iodides were heated with tnphenylphosphine in the absence of solvent to form the necessary phosphonium salts Direct deprotonation with butyllithium or lithium dusopropy-lamide did not lead to y hde formation, rather, deprotonation was accompanied by loss of fluonde ion However deprotonation with hydrated potassium carbonate in dioxane was successful and resulted in fluoroolefin yields of45-80% [59] (equation 54) p-Fluorinated ylides may also be prepared by the reaction of an isopropyli-denetnphenylphosphine yhde with a perfluoroalkanoyl anhydride The intermediate acyl phosphonium salt can undergo further reaction with methylene tnphenylphosphorane and phenyllithium to form a new ylide, which can then be used in a Wittig olefination procedure [60] (equation 55) or can react with a nucleophile [61] such as an acetylide to form a fluonnated enyne [62] (equation 56)... 

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