Acetone, enolization products from

Other possible ambident nucleophiles include cyanii anion (CN ), methyl sulfinate anion (CH3SO2 ), ar acetone enolate (CH3COCH2 ). Identify the most electro rich atom(s) in each anion (based on charges alone), ar indicate the major product that should result from an S, reaction with methyl bromide at this atom(s). 

The high selectivity of the catalyst in forming ( )-alkenes can be used in interesting ways (eq. 1). For example, in acetone-iie solution, within 15 min at room temperature allyl alcohol is converted to nearly pure enol (E)-26. Under these mild conditions, the product slowly isomerizes to the more stable aldehyde tautomer. We know of one other report of rapid enol formation from allyl alcohol, using a Rh... 

The enolate ions from acyclic and cyclic aliphatic ketones, and mainly those derived from acetone and pinacolone, are the carbanions most extensively studied so far. In general, the substitution products are obtained in good yield under irradiation in both liquid ammonia and dimethylsulfoxide (DMSO). For example, the anti-inflammatory drug fluorobiprophen 1 can be synthesized by the reaction of... 

The photoinitiated reaction of diethylphosphite ion with iodobenzene has been examined in different solvents [60]. The reaction of acetone enolate ion with 2-chloroquinoline, under the same irradiation times, suffers a strong dependence on solvent nature. Thus, the yield of substitution product decreases going from liquid ammonia (90%) to THF (82%), DMF (74%), dimethoxyethane (28%), diethyl ether (9%), or benzene (4%) [61]. For this reason, the reactions are usually performed in liquid ammonia or DMSO under irradiation. 

The anion of nitromethane (31) failed to react with Phi under irradiation in DMSO, as was the case with 1-AdI. However, when the reaction was carried out in the presence of acetone (27a) or pinacolone (27b) enolate ions, l-phenyl-2-nitroethane (161) was formed as major product, together with small amounts of benzene and toluene (equation 104). No products from the coupling with the ketone enolate ions were found169... 

Alkenes add photochemically to naphthalenes, normally to give products from 1.2 addition to the ring. In a report which appears to be a further example of this reaction Chow and co-workers reveal that Irradiation of mixtures of naphthols. or their methyl ethers, and acetyl acetone yield products derived from 1,2 addition of the enol form of the diketone to the naphthalene ring. Thus 1-naphthol gives the cyclobutanol (109) which retro-aldolises to the isolated product (110). However, the authors show that the excited state involved is In... 

A synthetic equivalent is a reagent whose structure, when incorporated into a product, gives the appearance of having come from one type of precursor when as a reactant it actually had a different structural origin. Although it is possible to form the enolate of acetone, use of ethyl acetoacetate as a synthetic equivalent is often more convenient because its a hydrogens are so much more acidic (pA = 9-11) than those of acetone itself (p. = 19-20). If we had wanted to use the acetone enolate directly, we would have had to use a much stronger base and other special conditions (e.g., a lithium enolate. Section 18.4). 

The general reaction procedure and apparatus used are exactly as described in Procedure 2. Ammonia (465 ml) is distilled into a 2-liter reaction flask and to this is added 165mlofisopropylalcoholandasolutionof30g(0.195 mole) of 17/ -estradiol 3-methyl ether (mp 118.5-120°) in 180 ml of tetrahydrofuran. The steroid is only partially soluble in the mixture. A 5 g portion of sodium (26 g, 1.13 g-atoms total) is added to the stirred mixture and the solid dissolves in the light blue solution within several min. As additional metal is added, the mixture becomes dark blue and a solid (matted needles) separates. Stirring is inefficient for a few minutes until the mass of crystals breaks down. All of the sodium is consumed after 1 hr and 120 ml of methanol is then added to the mixture with care. The product is isolated as in Procedure 4h 2. After being air-dried, the solid weighs 32.5 g (ca. 100% for a monohydrate). A sample of the material is dried for analysis and analyzed as described in Procedure 2 enol ether, 91% unreduced aromatics, 0.3%. The crude product may be crystallized from acetone-water or preferably from hexane. 

C-H insertion also occurs in the reactions with acetone and acetophenone, presumably through the rearrangement of transient OH-substituted phosphi-ranes [87]. C-C insertions occur for diketones to give 45 and have been postulated to occur via initial 1,2-addition to the conjugated enol 44 [87]. Diimines 46 also undergo C-C insertions [88]. Based on a theoretical evaluation, the products 47 are considered to result from a 2,3-sigmatropic rearrangement of initial formed P,N-ylids. 

Reaction of the enatiopure aldehyde 2-800, obtained from the corresponding imine by enantioselective hydrogenation, with Meldrum s acid (2-801) and the enol ether 2-802a (E/Z= 1 1) in the presence of a catalytic amount of ethylene diammonium diacetate for 4h gave 2-805 in 90 % yield with a 1,3 induction of >24 1. As intermediates, the Knoevenagel product 2-803 and the primarily produced cycloadduct 2-804 can be supposed the latter loses C02 and acetone by reaction with water formed during the condensation step (Scheme 2.178). 

The products described in Chart 2 clearly derive from two sites of acetone reactivity that can be identified with the carbonyl and a-carbon centers, as they are revealed by the reversible transfer of a proton from the a-carbon to oxygen. As such, enolization of the carbonyl compound represents a most fundamental change - an umpolung in which the keto acceptor (A) is interconverted to the enol donor (D) (equation 1). 

This procedure describes the preparation and use of an effective chiral catalyst for the asymmetric allylation of aldehydes. A previous synthesis of optically pure 1-(phenylmethoxy)-4-penten 2-ol requires seven steps from D-mannitol.4 This procedure has been employed successfully with other aldehydes,5 and also with methallyltributylstannane5 (see Table). Catalysts prepared from (R)- or (S)-BINOL and Ti(0-i-Pr)4 at 2 1 stoichiometry have also proven useful in these reactions.The olefinic products may be regarded as latent aldol products between aldehydes and the enolate of actetaldehyde or acetone. In all cases examined thus far, enantioselectivity... 

The Mannich reaction is best discussed via an example. A mixture of dimethylamine, formaldehyde and acetone under mild acidic conditions gives N,N-dimethyl-4-aminobutan-2-one. This is a two-stage process, beginning with the formation of an iminium cation from the amine and the more reactive of the two carbonyl compounds, in this case the aldehyde. This iminium cation then acts as the electrophile for addition of the nucleophile acetone. Now it would be nice if we could use the enolate anion as the nucleophile, as in the other reactions we have looked at, but under the mild acidic conditions we cannot have an anion, and the nucleophile must be portrayed as the enol tautomer of acetone. The addition is then unspectacular, and, after loss of a proton from the carbonyl, we are left with the product. 

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