Acetone anion

Removal of an a-hydrogen atom of the ketone as a proton to form n carbauion (acetone anion) ... 

Reaction of the cnrbaiilon (acetone anion) with the carbonyl carbon of ethyl acetate, accompanied by the release of an ethoxide ion, to form acetyl-acetone ... 

The acetoacetate enolate ion (A in frame 54) is a reagent for the synthon B, the acetone anion. We shall discover how to add the COiEt activating group later. 

Now we can disconnect the ketone using our synthetic equivalent for the acetone anion ... 

When two resonance forms are nonequivalent, the actual structure of the resonance hybrid is closer to the more stable form than to the less stable form. I bus, we might expect the true structure of the acetone anion to be closer to the resonance form that places the negative charge on an electronegative oxygen atom than to the form that places the charge on a carbon atom. 

Look back at the resonance forms of the acetate ion and the acetone anion shown in the previous section. The pattern seen there is a common one that leads to a useful technique for drawing resonance forms. In general, any three-atom grouping with a p orbital on each atom has two resonance forms. 

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... 

Resolution (enantiomers), 307-309 Resonance, 43-47 acetate ion and, 43 acetone anion and. 45 acyl cations and, 558 allylic carbocations and, 488-489 allylic radical and, 341 arylamines and, 924 benzene and, 44. 521 benzylic carbocation and, 377 benzylic radical and, 578 carbonate ion and. 47 carboxylate ions and, 756-757 enolate ions and, 850 naphthalene and, 532 pentadienyl radical and. 48 phenoxide ions and, 605-606 Resonance effect, 562 Resonance forms, 43... 

In principle, numerous reports have detailed the possibility to modify an enzyme to carry out a different type of reaction than that of its attributed function, and the possibility to modify the cofactor of the enzyme has been well explored [8,10]. Recently, the possibility to directly observe reactions, normally not catalyzed by an enzyme when choosing a modified substrate, has been reported under the concept of catalytic promiscuity [9], a phenomenon that is believed to be involved in the appearance of new enzyme functions during the course of evolution [23]. A recent example of catalytic promiscuity of possible interest for novel biotransformations concerns the discovery that mutation of the nucleophilic serine residue in the active site of Candida antarctica lipase B produces a mutant (SerlOSAla) capable of efficiently catalyzing the Michael addition of acetyl acetone to methyl vinyl ketone [24]. The oxyanion hole is believed to be complex and activate the carbonyl group of the electrophile, while the histidine nucleophile takes care of generating the acetyl acetonate anion by deprotonation of the carbon (Figure 3.5). 

Following a newly discovered indole synthesis, it has been shown that photochemical reaction of acetone anion with 3-amino-2-chloropyridine in liquid ammonia gives 2-methylpyrrolo[3,2-6]pyridine in 45% yield (80JOC1546). 

The chiral organocopper compound (186) adds diastereoselectively to 2-methyl-2-cyclopentenone, allowing the preparation of optically active steroid CD-ring building blocks (Scheme 68).202-204 A related method was applied to a synthesis of the steroid skeleton via an intramolecular (transannular) Diels-Alder reaction of a macrocyclic precursor.203 Chiral acetone anion equivalents based on copper azaeno-lates derived from acetone imines were shown to add to cyclic enones with good selectivity (60-80% ee, after hydrolysis).206-208 Even better ee values are obtained with the mixed zincate prepared from (187) and dimethylzinc (Scheme 69). Other highly diastereoselective but synthetically less important 1,4-additions of chiral cuprates to prochiral enones were reported.209-210... 

AN UNSHARED PAIR OF ELECTRONS NEXT TO A PI BOND 0 ACETATE ANION, ACETIC ACID, 0 ACETONE ANION. 

This is an example of an aldol condensation between an acetone anion and acetaldehyde. Note the mechanism proceeds through addition of an anion to an aldehyde carbonyl. Arrow pushing is illustrated below ... 

The second stage of the reaction is addition of the acetone anion to formaldehyde as shown below. 

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