chemistry

Intramolecular reactions of diazocarbonyl compounds

Intramolecular reactions of diazocarbonyl compounds is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Intramolecular reactions of diazocarbonyl compounds rather than just read about it. In short: Intramolecular reactions of diazocarbonyl compounds include addition to carbon–carbon double bonds to form fused cyclopropanes and insertion into carbon–hydrogen bonds or carbon–carbon bonds. Introduction In the presence of an appropriate transition metal (typically copper or rhodium), α-diazocarbonyl compounds are converted to transition metal carbenes, which undergo addition reactions in the presence of carbon–car…

Key takeaways

Intramolecular reactions of diazocarbonyl compounds belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Intramolecular reactions of diazocarbonyl compounds to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Intramolecular reactions of diazocarbonyl compounds from memory before moving on to harder problems.

Reference excerpt

Intramolecular reactions of diazocarbonyl compounds include addition to carbon–carbon double bonds to form fused cyclopropanes and insertion into carbon–hydrogen bonds or carbon–carbon bonds.

Introduction In the presence of an appropriate transition metal (typically copper or rhodium), α-diazocarbonyl compounds are converted to transition metal carbenes, which undergo addition reactions in the presence of carbon–carbon double bonds to form cyclopropanes. Insertion into carbon–carbon or carbon–hydrogen bonds is possible in substrates lacking a double bond. The intramolecular version of this reaction forms fused carbocycles, although yields of reactions mediated by copper are typically moderate. For enantioselective cyclopropanations and insertions, both copper- and rhodium-based catalysts are employed, although the latter have been more heavily studied in recent years.

(1)

Mechanism and stereochemistry

Prevailing mechanism The reaction mechanism of decomposition of diazocarbonyl compounds with copper begins with the formation of a copper carbene complex. Evidence for the formation of copper carbenes is provided by comparison to the behavior of photolytically generated free carbenes and the observation of appreciable enantioselectivity in cyclopropanations with chiral copper complexes. Upon formation of the copper carbene, either insertion or addition takes place to afford carbocycles or cyclopropanes, respectively. Both addition and insertion proceed with retention of configuration. Thus, diastereoselectivity may often be dictated by the configuration of the starting material.

(2)

Scope and limitations Either copper powder or copper salts can be used very generally for intramolecular reactions of diazocarbonyl compounds. This section describes the different types of diazocarbonyl compounds that may undergo intramolecular reactions in the presence of copper. Note that for intermolecular reactions of diazocarbonyl compounds, the use of rhodium catalysts is preferred. Diazoketones containing pendant double bonds undergo cyclopropanation in the presence of copper. The key step in one synthesis of barbaralone is the selective intramolecular cyclopropanation of a cycloheptatriene.

(3) α,β-Cyclopropyl ketones may act as masked α,β-unsaturated ketones. In one example, intramolecular participation of an aryl group leads to the formation of a polycyclic ring system with complete diastereoselectivity.

(4) α-Diazoesters are not as efficient as diazoketones at intramolecular cyclizations in some cases because of the propensity of esters to exist in the trans conformation about the carbon–oxygen single bond. However, intramolecular reactions of diazoesters do take place—in the example in equation (5), copper(II) sulfate is used to effect the formation of the cyclopropyl ester shown.

(5) In the presence of a catalytic amount of acid, diazomethyl ketone substrates containing a pendant double bond or aryl group undergo cyclization. The mechanism of this process most likely involves protonation of the diazocarbonyl group to form a diazonium salt, followed by displacement of nitrogen by the unsaturated functionality and deprotonation. In the example below, demethylation affords a quinone.

(6) When no unsaturated functionality is present in the substrate, C-H insertion may occur. C-H Insertion is particularly facile in conformationally restricted substrates in which a C-H bond is held close to the diazo group.

(7) Transannular insertions, which form fused carbocyclic products, have also been observed. Yields are often low for these reactions, however.

(8) Insertion into carbon–carbon bonds has been observed. In the example in equation (9), the methyl group is held close to the diazo group, facilitating C-C insertion.

(9)

Synthetic applications Intramolecular cyclopropanation of a diazoketone is applied in a racemic synthesis of sirenin. A single cyclopropane diastereomer was isolated in 55% yield after diazoketone formation and cyclization.

(10)

Experimental conditions and procedure

Typical conditions Diazo compounds may be explosive and should be handled with care. Very often, the diazocarbonyl compound is prepared and immediately used via treatment of the corresponding acid chloride with an excess of diazomethane (see Eq. (18) below for an example). Reactions mediated by copper are typically on the order of hours, and in some cases, slow addition of the diazocarbonyl compound is necessary. Reactions should be carried out under an inert atmosphere in anhydrous conditions.

Example procedure Source:

… excerpt ends here. Continue reading the full article.

Illustrations

Intramolecular reactions of diazocarbonyl compounds illustration

Worked examples

Example 1 — a first encounter with Intramolecular reactions of diazocarbonyl compounds

Start with the simplest possible case. Write down what Intramolecular reactions of diazocarbonyl compounds claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Intramolecular reactions of diazocarbonyl compounds before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Intramolecular reactions of diazocarbonyl compounds ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Intramolecular reactions of diazocarbonyl compounds

In research: Intramolecular reactions of diazocarbonyl compounds appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Intramolecular reactions of diazocarbonyl compounds in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Intramolecular reactions of diazocarbonyl compounds is common in secondary-school and first-year university syllabi. It links to neighbouring topics Organic reactions, so understanding it makes those chapters shorter.
In everyday life: Look for Intramolecular reactions of diazocarbonyl compounds outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Intramolecular reactions of diazocarbonyl compounds” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Intramolecular reactions of diazocarbonyl compounds in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Intramolecular reactions of diazocarbonyl compounds means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Intramolecular reactions of diazocarbonyl compounds out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Intramolecular reactions of diazocarbonyl compounds in simple terms?

Intramolecular reactions of diazocarbonyl compounds include addition to carbon–carbon double bonds to form fused cyclopropanes and insertion into carbon–hydrogen bonds or carbon–carbon bonds. Introduction In the presence of an appropriate transition metal (typically copper or rhodium), α-diazocarbo…

Why does Intramolecular reactions of diazocarbonyl compounds matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Intramolecular reactions of diazocarbonyl compounds?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Intramolecular reactions of diazocarbonyl compounds.