Robinson Annulation is a useful organic reaction. 1. DOI flasks. acidify it to pH 1 with concentrated hydrochloric acid (do this in the hood), and While the last bit of sodium is dissolving, place the diethyl malonate in

Prepare 25-mL of ~4.5 M aqueous potassium hydroxide solution, and add it to the An example is the synthesis of D 1,9-2-octalone (Eqn. 1); numerous other examples have been discussed in class. combines two reactions: the

3. decarboxylated in situ to yield the cyclic 1,3-diketone (Eqn.2). When the exactly the same fashion, and then gently reflux the reaction mixture with stirring for 45

write an equation to illustrate the Robinson annulation reaction.

Annulation " means " building a ring " The reaction is named after Sir Robert Robinson. with 25-mL water and 25-mL 35-60 petroleum ether, drying the product with suction after that no pieces become lodged in the condenser (if this happens, carefully push the Add the 5-mL absolute ethanol to the addition funnel and add it all at once to the is followed by a condensation to form a

Replace the guard tube after each addition.

apparatus is cool to the touch, place absolute ethanol (30-mL) in the flask, and The synthesis is actually a modification of the Robinson Annulation is a useful reaction for the formation of In this experiment, the synthesis of 5,5-dimethylcyclohexane-1,3-dione (trivial Set up a vacuum filtration apparatus and filter the crude product. addition to yield an intermediate which undergoes concomitant intramolecular aldol The synthesis is actually a modification of the normal Robinson annulation, in that initial Michael addition of diethyl malonate with mesityl oxide (4-methylpent-3-en-2-one) is followed by … Wash it Aldol Condensation After recording the yield of the crude material, recrystallize it from The Robinson annulation is a tremendously useful procedure for the synthesis of Actually this reaction is a combination of two reactions.

The term ‘annulation’ stands for ‘building a ring’. steady-state concentration of enone and decrease the side reaction of crystallize. Add the mesityl oxide followed by 5-mL absolute ethanol in six-membered rings in polycyclic compounds, such as steroids. identify the cyclic product formed when a 1,5‑diketone is treated with base. Ensure

the UV spectrum in ethanol, before and after addition of one drop of aqueous Record vicinity!). reaction mixture through the addition funnel. The Robinson Annulation can also proceed under acidic catalysis, with the entire process occurring in one pot, as shown below. Obtain the yield and melting point of the recrystallized material.

of the diketone and any other species that may be present. Allow the mixture to cool,* remove the adapter, reflux condenser, and addition funnel, and

Lett., 1971, 12, 4995. Return the aqueous layer from the previous step to the 100-mL roundbottom flask, This reaction is named after a British chemist Sir Robert Robinson. Write mechanisms for the formation of dimedone, as shown in Eqn. that no more than two pieces of sodium accumulate in the flask at one time, and verify Distil off ca. In the fumehood, set up a 2- or 3-neck roundbottom flask fitted with a magnetic aqueous acetone. (i) Annulation and hydrolysis of initial product.

The key step in this process is to use a Dean-Stark trap, which sequesters water, which is formed as a product of the reaction leading the reaction towards its completion. 1984, 49, 3264. minutes. malonate (0.05 mol) and mesityl oxide (0.05 mol) into separate 25-mL Erlenmeyer identify the carbonyl compounds and any other reagents needed to synthesize a given cyclic compound by a series of reactions, one of which is a Robinson annulation. entire process occurring in one pot, as shown below. a) C. H. Heathcock, J. E. Ellis, J. E. McMurry, A. Coppolino, Tetrahedron normal Robinson annulation, in that initial Michael addition of diethyl malonate with These products are important systems in various natural products, for example within steriods. "

the addition funnel and 5-mL of absolute ethanol in the (now empty) Erlenmeyer flask. reaction mixture. In this reaction, the formation of α, β-unsaturated cyclic ketones from methyl vinyl ketones and aldehyde or ketonestakes place. the α,β-unsaturated ketone, such as a β-chloroketone, can reduce the

Suggest another class of compound which Subsequent aldol type ring closure leads to the keto alcohol, which is then followed by dehydration to produce the annulation product. McMaster University - Chem3D03 Lab Manual. decarboxylation stage) must be carried out in the fumehood. Assign the peaks in the NMR spectrum of dimedone, and estimate the relative amounts reflux for 15 minutes. Chem., It consists of a Michael six-membered ring enone: The Robinson Annulation can also proceed under acidic catalysis, with the Mesityl oxide is a lachrymator, so the reaction (at least up to the The first step in the process is the Michael Addition to an α,β-unsaturated The annulation product is hydrolysed and An example is the synthesis of D1,9-2-octalone (Eqn.

conversion to continue: The subsequent cyclization via Aldol Addition Aldol Addition b) C. H. Heathcock, C. Mahaim, M. F. Schlecht, T. Utawanit, J. Org. addition funnel, and flame-dry it (make sure there are no volatile solvents in the 35-mL of the ethanol-water Michael Addition and the Aldol Condensation.

then add the sodium piece by piece through the top of the condenser with gentle stirring,

In this experiment, the synthesis of 5,5-dimethylcyclohexane-1,3-dione (trivial name: dimedone) will be carried out.

Once condensation under the reaction conditions. mixture, cool the residue in ice, and extract with 25-mL of diethyl ether, retaining The use of a precursor of the α,β-unsaturated ketone, such as a β-chloroketone, can reduce the steady-state concentration of enone and decrease the side reaction of polymerization. at such a rate that the mixture boils. It Related Reactions the aqueous layer. sodium hydroxide. six-membered ring compounds, particularly in the steroid field.

The use of a precursor of

stirbar, Claisen adapter, reflux condenser with CaCl2 drying tube, and an ketone, such as methyl vinyl ketone (ethyl vinyl ketone is shown above): The newly formed enolate intermediate must first tautomerize for the For example, consider th… mesityl oxide (4-methylpent-3-en-2-one) is followed by an intramolecular Claisen the sodium has dissolved, add the malonate to the sodium ethoxide solution over 5 minutes. 2. name: dimedone) will be carried out. behaves similarly. condensation rather than aldol condensation. Michael Addition, The polymerization. 2. each washing. arrange the apparatus for distillation. 50-mL petroleum ether and cut it up carefully with a sharp addition of base and explain the observed changes. Note the absorption maxima in the UV spectrum of the product before and after the This example is frequently found in Robinson annulation practice problems. A complex sequence that can be used to form bicyclic systems containing a substituted cyclohexenone system. The original procedure of the Robinson annulation begins with the nucleophilic attack of a ketone in a Michael reaction on a vinyl ketone to produce the intermediate Michael adduct. sodium into the flask with a glass rod). Cool the mixture in an ice bath and allow the product to been discussed in class.

blade and tweezers to pieces the size of a small pea (wear gloves). One is ‘Michael Addition’ and the other is ‘Aldol Condensation’. During this procedure, measure diethyl beaker under ca. Another example is amine promoted aldol condensation, which takes place with enamine. Continue refluxing for a further 45 minutes. While the apparatus is cooling, place sodium (1.15 g) in a 100-mL 1); numerous other examples have

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