Markovnikov addition product

Problem 13.12 We saw in Section 8.3 that addition of HBr to a terminal alkyne leads to the Markovnikov addition product, with the Br bonding to the more highly substituted carbon. How could you use 13C NMR to identify the product of the addition of 1 equivalent of HBr to 1-hexyne ... 

The hydroaminations of electron-deficient alkenes with aniline or small primary alkylamines proceed at high conversions (85-95%, nnder mild conditions, 5 mol%, rt), giving exclnsively the anh-Markovnikov addition product. Secondary dialkyl or bnlky primary amines require longer reaction times. With amines containing P-hydrogens, no imine side-products were observed. 

The first example of hydroamination of styrene in the presence of an alkali metal appeared in a patent in 1948, albeit with a low catalytic activity (Eq. 4.30) [149]. The anti-Markovnikov addition product was obtained. 

Although zirconium bisamides Cp2Zr(NHAr)2 do not catalyze the hydroamination of alkenes (see above), they are catalyst precursors for the hydroamination of the more reactive double bond of allenes to give the anti-Markovnikov addition product (Eq. 4.96) [126]. 

Similar to the addition of secondary phosphine-borane complexes to alkynes described in Scheme 6.137, the same hydrophosphination agents can also be added to alkenes under broadly similar reaction conditions, leading to alkylarylphosphines (Scheme 6.138) [274], Again, the expected anti-Markovnikov addition products were obtained exclusively. In some cases, the additions also proceeded at room temperature, but required much longer reaction times (2 days). Treatment of the phosphine-borane complexes with a chiral alkene such as (-)-/ -pinene led to chiral cyclohexene derivatives through a radical-initiated ring-opening mechanism. In related work, Ackerman and coworkers described microwave-assisted Lewis acid-mediated inter-molecular hydroamination reactions of norbornene [275]. 

Electron-donor sensitisers such as 1-methoxynaphthalene (forming the Markovnikov addition product) ... 

The reaction of / with bromine in carbon tetrachloride confirms the prediction that / is an alkene. The reaction with HBr means that G is the Markovnikov addition product, and the reaction in the presence of peroxides makes //the anti-Markovnikov product. 

The indenylidene complexes IX and XXVIIIc were also reported to promote the addition of different carboxylic acids to terminal alkynes to give enol esters, the Markovnikov addition product being the major product with, in some cases, the competing catalytic dimerization of terminal alkynes [61]. 

The literature prior to the observation of competitive free radical processes initiated by peroxides and/or light is often contradictory. When the reaction is properly carried out, however, high yields of Markovnikov addition products can be achieved from a wide variety of simple alkenes (equations 68-7 j) 6i,tot.ios-1 ii Unsymmetrical alkenes such as 2-pentene give mixtures of regioisomers.112-114... 

A hydroformylation reaction in diene polymers introduces a formyl group which is an extremely reactive functional group. Sibtain and Rempel [65] carried out hydroformylation of SBR using HRh(CO)(PPh3)3 and reported anti-Markovnikov addition product. Hydroformylation takes place preferentially in the 1,2 unit. As the degree of hydroformylation increases new absorption bands appear at 1724 cm"1 due to v(C=0) and at 2700 cm 1 due to v(C-H) in CHO. Bhattacharjee and co-workers [66] carried out hydroformylation of NBR and observed new peaks at 1724 and 2700 cm"1 which are characteristics of CHO groups. 

Addition reactions to unsymmetrical alkenes in which a reagent with the structure H—X transfers the H atom to the less-substituted C atom and the X group to the more substituted C atom give, according to an old nomenclature, a so-called Markovnikov addition product. On the other hand, addition reactions of reagents H—X in which the H atom is transferred to the more substituted C atom of an unsymmetrically substituted C=C double bond and the X group is transferred to the less substituted C atom lead to a so-called anti-Markovnikov addition product. 

Benzeneselenenyl chloride adds to alkynes to produce mixtures of tra/ts-alkene adducts. For example, the addition of benzeneselenenyl chloride to the alkyne (18) produces the alkene (19), which can be transformed to yield the unusual diene (20 equation 16). Alkynic alcohols give anti-Markovnikov addition products under kinetic control. The reaction is thought to proceed through the selenirenium ion (21 equation 17). Selenium electrophiles add to a, 3-alkynic cariranyl moieties to produce cis adducts in good yield (equation 18). ... 

Improved results were achieved when trichlorosilane was treated with alkenes in the presence of a ferrocenyl-palladium catalyst, [(7 )-(5)-PPFA]PdCl2 8a. In the ease of unsymmetrica alkenes, Markovnikov addition products are formed. 

If, in the presence of hypochlorous acid, cr-pinene is to behave as 1-meth-ylcyclohexene does, that is, yielding chiefly Markovnikov addition products... 

Olefinic pyrazines like 108 were shown to react with QH in the superacid TfOH to give anti-Markovnikov addition products like 109 <050L2505>. The orientation observed is presumed to be due to the multiply charged heterocycle adjacent to the olefin. Pyrazine o-quinodimethanes underwent Diels-Alder condensation with meso-tetraarylporphyrins to give new jt-extended porphyrins <05TL2189>. A one-pot formation of polycyclic - and -lactones like 111 was developed using the reaction of pyridine and pyrazine (110) with bis(trimethylsilyl)ketene acetals. Many of them were characterized by X-ray <05EJO3724>. 

When predicting the product of a reaction, you have to recall what you know about the kind of reaction being carried out and then apply that knowledge to the specific case you re dealing with. In the present instance, recall that the two methods of hydration—hydroboration/oxidation and oxymercura-tion—give complementary products. Hydroboration/oxidation occurs with syn stereochemi. itiy and gives the non-Markovnikov addition product oxymercuration gives the Markovnikov product. 

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