Which reaction obeys the markovnikov rule

This Pd II -catalyzed allylic acetoxylation was investigated with a number of alkenes under aerobic conditions Table 5. Nearly all the substrates examined resulted in good yields of the linear acetoxylation products. This aerobic ligand-based strategy serves as an inspiration for future work on the role of ancillary ligands in Pd II -catalyzed oxidation and accordingly, omission of the use of undesirable oxidants.

Lin et al. This aerobic Pd II -catalyzed oxidation is an attractive method for the bioactive synthesis of natural products Scheme 6. The steric demand of nucleophiles is considered as another potential factor to influence the regioselectivity. In , Kataoka et al. The terminal acetals can undergo acid-catalysed hydrolysis to result in the corresponding aldehydes.

The proposed mechanism for this acetalization is shown in Scheme 7. The nucleophilic attack of the pinacol in an anti-Markovnikov manner then afforded the benzyl intermediate. Attack on the internal carbon would be unfavourable due to the steric repulsion between the phenyl group and pinacol. The formation of a benzyl intermediate in this process is considered to be the main factor leading to anti-Markovnikov selectivity. Although regioselectivity control by means of a bulky solvent is effective in Kataoka's system, the acetalization method is still an indirect way of obtaining the aldehyde.

Recently, a facile Pd II -catalyzed process to convert olefins directly into aldehydes was achieved by Grubbs et al. Due to the bulkiness of t -BuOH, the linear vinyl ether is preferred, which constitutes the key factor for high anti-Markovnikov selectivity. During the process, acid is generated in the presence of water, upon which the vinyl ether is converted to aldehyde via acid-catalyzed hydrolysis Fig.

This highly aldehyde-selective system shows a major improvement to current methods for Wacker oxidation. The by-product 1,4-hydroquinone HBQ in this reaction could be easily converted to 1,4-benzoquinone BQ via aerobic oxidation. More recently, Grubbs et al. In this system, AgNO 2 plays a key role in the significant improvement of selectivity and yield. MeNO 2 was found to be an important co-solvent. Good functional-group tolerance was observed with the optimized conditions.

Thus the mechanistic feature of this reaction was proposed to be a metal-mediated radical-type addition to terminal olefins by NO 2 species Scheme 8. The success of this system provides a crucial lead for further development of catalytic anti-Markovnikov oxidation systems using unbiased aliphatic substrates. Later on, the authors further extended the study to the ketone synthesis from the more challenging internal olefins by Wacker-type oxidation.

In fact, substrate control is an inherent challenge for Wacker-type processes. Sigman and Werner made efforts to develop a useful catalyst-controlled oxidation method which is not affected by functional groups on olefins or steric effects of solvents.

It is believed that the electron-poor quinoline module of the ligand facilitates olefin coordination Scheme 9. Markovnikov selectivity is achieved here. The use of an electronically asymmetric ligand in this Wacker oxidation has been shown to critically affect the environment of the metal center. Thus ligand design is crucial to achieve catalyst control for Wacker-type process and provides insight to realizing more challenging anti-Markovnikov functionalization.

Apart from the widely known Wacker-type methods for synthesizing aldehydes from olefins, Che et al. Lahiri et al. In summary, Che's ruthenium- and Lahiri's iron-catalyzed systems provide unique and efficient methods for aldehyde synthesis from terminal olefins, which significantly complements the conventional Wacker-type oxidation.

The proposed mechanism involves the formation of a hydrido-Pt II -hydroxo complex, followed by protonation to form an aqua complex and subsequent coordination of the olefin to platinum. The hydroxide anion then attacks the coordinated olefin to form a Pt-alkyl complex which then undergoes trans — cis isomerization resulting in the alkyl and hydride moiety being cis to one another. The complex then undergoes C—H reductive elimination to yield the primary alcohol Scheme Despite the elegance of Trogler's method, the system was subsequently claimed to be irreproducible by Ramprasad et al.

In common with Grushin, Parkins et al. In consideration of the unusual method adopted by Trogler for the preparation of the catalyst precursor trans -[ Me 3 P 2 PtHCl], Parkins et al. Although these conditions corresponded most closely to that reported by Trogler, no 1-octanol was detected.

The impurity underwent a Hock rearrangement and 1-methoxyvinyloxyhexane was formed as shown in Scheme It was suspected that Trogler's catalytic system 32 might have contained some trinuclear species. However, the anti-Markovnikov product 1-methoxyoctane was observed in the product mixture. This suggests that a reaction between the hydroperoxide impurities in 1-octene and the trinuclear platinum cluster occurred, leading to the formation of 1-methoxyoctane as the product instead.

The proposed mechanism for 1-methoxyoctane production from 1-octene is shown in Scheme Due to the presence of varying amounts of hydroperoxide impurities in treated or untreated 1-octene, Parkins et al. However, their studies shed some light on the problems of the platinum-catalyzed anti-Markovnikov hydration of terminal olefins initially reported by Trogler.

In , Toste et al. The proposed catalytic cycle is shown in Scheme The phosphonium enolate is formed by nucleophilic attack from the phosphine to the unsaturated carbonyl compound, which spontaneously generates the alcohol by deprotonation.

The alkoxide of the phosphonium ion pair then undergoes subsequent addition to give an enolate ion pair. Recently, a tandem catalyst system for the synthesis of primary alcohols from non-activated terminal olefins was reported by Grubbs et al. This triple-relay system relies on three criteria, firstly, the oxidation step must be aldehyde-selective; secondly, the oxidation cycle must be compatible with the reduction cycle and thirdly, the migration of the hydride from Pd to Ru must be facile.

Any nucleophile in solution will then attack the positive carbon no matter where it is. Reactions that show anti-Markovnikov regioselectivity have another driving factor and do NOT show a carbocation intermediate. Which mnemonic did you have memorized for Markovnikov's Rule? Do you feel better about it now that you fully understand? Let me know in the comments below. Your videos are extremely helpful! Thank you for all the time and effort that you put into them! Hi Leah- Love the content.

I believe u wrote it the opposite but I am not sure. Thank you so much! Thanks again! Great article! It clarified a few things for me. I loved the way you organized your content. Could you clarify the following?

Your email address will not be published. Save my name, email, and website in this browser for the next time I comment. The true key to successful mastery of alkene reactions lies in practice practice practice. However, … [Read More Click for additional cheat sheets. Click for additional MCAT tutorials. Click for additional orgo tutorial videos. Regioselectivity Regioselectivity means that a chemical reaction can occur in many different ways, but chooses to follow one particular path. Method 2: Hydrogen goes to the less substituted carbon.

All of these mnemonics are great for memorizing the reaction. Instead we are adding both a halogen and an OH group… Which is the nucleophile? WHY do the halogens add to the more substituted carbon atom? Therefore, the less stable the intermediate, the slower or less likely it will form a product.

So, what intermediate are we referring to? Carbocation formation While Carbocations are not very stable they will form under certain conditions. Can they both form? Remember, opposites attract. This is how we get the product. So what ultimately made the difference?

The carbocation intermediate. Halogen simply followed. In short: The nucleophile will add to the carbon that can form the most stable carbocation intermediate.

When looking at an alkene reaction, ask yourself the following two questions: Will this reaction undergo a carbocation intermediate?

Yes or no? If yes, which carbon would be the most stable carbocation? What about Anti-Markovnikov Addition? But how are these reactions correlated?

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