Alkenes into alcohols

Isohypsic reactions of alkenes, like electrophilic additions of H2O or HX, represent a conventional pathway for the preparation of alcohols and alkyl halides from alkenes. The scope of their application was originally limited as unsymmetrical alkenes (e.g. 125) gave product mixtures composed of both Markovnikov (M) adducts and anti-Markovnikov (aM) adducts. As was already mentioned above (see Scheme 2.10), an efficient and general method for the conversion of alkenes into alcohols or ethers 126 (Scheme 2.47), with a nearly complete M selectivity, was elaborated using mercury salts as electrophiles in conjunction with the reduction of the formed adducts. It is also... 

Another secondary borane useful for the conversion of alkenes into alcohols and of alkynes to aldehydes or ketones is catecholborane (1,3,2-benzodioxaborole), which is prepared from catechol and borane in tetrahydrofuran [1201] (equations 600 and 601). 

Conversion of Alkenes into Alcohols by Hydroboralion Followed by Oxidation 184 ... 

Hydroboration-oxidation, then, converts alkenes into alcohols. Addition is highly regiospecific the preferred product here, however, is exactly opposite to the one formed by oxymercuration-demercuration or by direct acid-catalyzed hydration. For example ... 

Diborane is widely used in organic chemistry (hydroboration) to convert alkenes into alcohols. Consult an organic book and show reactions for this conversion. What is the advantage of this method ... 

Hydroboration-Oxidadon (Section 6.4) BH3 followed by basic HjOj converts alkenes into alcohols with non-Markovnikov regioselectivity (the OH adds to the less substituted alkene carbon) and syn stereoselectivily without rearrangement. The reaction is stereospedfic because as-alkenes give different products than do frans-alkenes.The mechanism involves coordination of the alkene tt bond to the vacant 2p orbital of borane followed by a four-membered ting transition state, which simultaneously adds H to the mote substituted carbon and boron to the less substituted alkene carbon. The basic peroxide replaces the boron with OH. 

Otymercuration (Section 10.3) The mercury-catalyzed conversion of alkenes into alcohols. Addition is in the Markovnikov sense, and there are no rearrangements. A three-membered ring containing mercury is an intermediate in the reaction. Alkynes also undergo oxymercuration to give enols that are rapidly converted into carbonyl compounds under the reaction conditions. 

The 4-hydroxy-1-alkene (homoallylic alcohol) 81 is oxidized to the hetni-acetal 82 of the aldehyde by the participation of the OH group when there is a substituent at C3. In the absence of the substituent, a ketone is obtained. The hemiacetal is converted into butyrolactone 83[117], When Pd nitro complex is used as a catalyst in /-BuOH under oxygen, acetals are obtained from homoallylic alcohols even in the absence of a substituent at C-3[l 18], /-Allylamine is oxidized to the acetal 84 of the aldehyde selectively by participation of the amino group[l 19],... 

The l,5-hexadien-3-ol derivatives 792 and 794 are cycli2ed to form the cyclo-pentadiene derivatives 793 and 795 by insertion of an alkene into -allylpalla-dium formed from allylic alcohols in the presence of trifluoroacetic acid (lO mol%) in AcOH[490],... 

Usually, organoboranes are sensitive to oxygen. Simple trialkylboranes are spontaneously flammable in contact with air. Nevertheless, under carefully controlled conditions the reaction of organoboranes with oxygen can be used for the preparation of alcohols or alkyl hydroperoxides (228,229). Aldehydes are produced by oxidation of primary alkylboranes with pyridinium chi orochrom ate (188). Chromic acid at pH < 3 transforms secondary alkyl and cycloalkylboranes into ketones pyridinium chi orochrom ate can also be used (230,231). A convenient procedure for the direct conversion of terminal alkenes into carboxyUc acids employs hydroboration with dibromoborane—dimethyl sulfide and oxidation of the intermediate alkyldibromoborane with chromium trioxide in 90% aqueous acetic acid (232,233). 

A Alkenes can be converted into alcohols by acid-catalyzed addition of water. Assuming that Vlarkovnikov s rule is valid, predict the major alcohol product from each of the following alkenes. 

RO then removes a proton from water, and the final product is an alcohol. Overall, we have a two-step synthesis for converting an alkene into an alcohol. This two-step... 

Early attempts by Asinger to enlarge the scope of hydroalumination by the use of transition metal catalysts included the conversion of mixtures of isomeric linear alkenes into linear alcohols by hydroalumination with BU3AI or BU2AIH at temperatures as high as 110°C and subsequent oxidation of the formed organoaluminum compounds [12]. Simple transition metal salts were used as catalysts, including tita-nium(IV) and zirconium(IV) chlorides and oxochlorides. The role of the transition metal in these reactions is likely limited to the isomerization of internal alkenes to terminal ones since no catalyst is required for the hydroalumination of a terminal alkene under these reaction conditions. 

Effective catalysts for heterogeneous oxidations using 02 are mainly Pt and Pd with some activity by Ir70 and Ru.71 Much work has gone into alcohol oxidations that are dehydrogenations to ketones or aldehydes. Also, oxygen may be inserted at allylic positions of alkenes and these may be dehydrogenated to ketones or aldehydes.72 In the case of aldehydes, additional oxidation may be accomplished to produce acids.72,73... 

Under certain conditions, the trifluoroacetic acid catalyzed reduction of ketones can result in reductive esterification to form the trifluoroacetate of the alcohol. These reactions are usually accompanied by the formation of side products, which can include the alcohol, alkenes resulting from dehydration, ethers, and methylene compounds from over-reduction.68,70,207,208,313,386 These mixtures may be converted into alcohol products if hydrolysis is employed as part of the reaction workup. An example is the reduction of cyclohexanone to cyclohexanol in 74% yield when treated with a two-fold excess of both trifluoroacetic acid and triethylsilane for 24 hours at 55° and followed by hydrolytic workup (Eq. 205).203... 

In contrast, the clean thermolysis of appropriately chosen ethers into alkene and alcohol components was little known until our work in this area demonstrated its applicability to transformations involving both side-chain ether groups [14] or the main chain of polyethers [11]. 

The perruthenate oxidation of alcohols has been incorporated into a one-pot conversion of alkenes into carbonyl compounds via their initial hydroboration [44], Overall yields can be as high as 98%. Where the initial alkene also contains carbonyl groups these are reduced in the first step and are reoxidized by the perruthenate. 

Phase-transfer generated diborane has been used for the hydroboration of alkenes and their conversion into alcohols [1,2] and the procedure has also been employed for the cleavage of formamido compounds to yield the amines [3]. Cyclododecan-1,3- and 1,4-diones have been obtained in a 3 1 ratio and overall yield of 59% via... 

Keto esters are obtained by the carbonylation of alkadienes via insertion of the alkene into an acylpalladium intermediate. The five-membered ring keto ester 22 is formed from l,5-hexadiene[24], Carbonylation of l,5-COD in alcohols affords the mono- and diesters 23 and 24[25]. On the other hand, bicy-clo[3.3.1]-2-nonen-9-one (25) is formed in 40% yield in THF[26], l, 5-Diphenyl-3-oxopentane (26) and l,5-diphenylpent-l-en-3-one (27) are obtained by the carbonylation of styrene. A cationic Pd-diphosphine complex is used as the catalyst[27]. 

A Co(II) Schiff-base complex converts 1- and 2-alkenes into methyl ketones and the corresponding secondary alcohols in the presence of oxygen or H2O2 in primary alcohol solvent.543 A radical oxidation with cobalt hydroperoxide through the formation and subsequent decomposition of alkyl hydroperoxide was suggested.543 An efficient conversion of alkenylarenes to ketones was achieved by the use of molecular oxygen and EtjSiH in the presence of a catalytic amount of Co(II) porphyrin in 2-propanol.544... 

According to this hypothesis, the results are modified from what would be expected from classical radical reactions. The interest in this hypothesis is that, with the sole exception of saturated hydrocarbons, it could apply to all the compounds that can be coordinated at the Tiiv center, such as alkenes, aromatics, alcohols, and sulfides. According to this hypothesis, the weak Lewis acidity of Tilv would help to bring the reactant into its coordination sphere. The initial coordination of the reactant would explain the oxidation of methyl-substituted aromatics in the aromatic ring and not in the side chain, even with a radical-type mechanism. 

Molybdenum and tungsten compounds have long been known to catalyze the transformations of alkenes into epoxides and diols by hydrogen peroxide.171"173 This reaction was found to be suitable for the epoxidation of water-soluble alkenes such as allylic alcohols (equation 30)174,175 or unsaturated carboxylic acids (equation 31).171 Tungsten catalysts were found to be more active and selective in aqueous solution than molybdenum complexes. 

Styrene derivatives can be selectively converted to the corresponding benzyl alcohols by molecular oxygen in the presence of bis(dimethylglyoximato)chloro(pyridine)cobalt(III) and sodium tetrahydroborate (equation 242).559 A likely mechanism for this reaction involves insertion of the alkene into the cobalt-hydride bond, followed by 02 insertion into the cobalt-carbon bond, as in equation (11), and decomposition of the peroxide adduct (168) to the ketone, which is reduced to alcohol by NaBH4 (equation 243). 

Collins reagent is used for the introduction of carbonyl groups at allylic positions." This transformation of alkenes into enones is much slower than the oxidation of alcohols, requiring a great excess of Cr03 2Py and prolonged reaction times. Consequently, alcohols can be oxidized to aldehydes and ketones by Collins reagent without interference from alkenes. 

Most functional groups resist Collins oxidation, including the oxidation-sensitive sulfides106 and thioacetals.103 Although Collins reagent can transform alkenes into enones" and alkynes into inones,107 these reactions are slower than the oxidation of alcohols into aldehydes or ketones. Therefore, alcohols can be usually oxidized with no interference from alkenes108 or alkynes.109... 

PDC is able to oxidize allylic positions, resulting in the transformation of alkenes into enones. This reaction normally demands heating and is best performed in solvents other than CH2CI2.140 Very often, r-butyl hydroperoxide is added.141 When a standard procedure for the oxidation of alcohols with PDC is employed, normally no interference with alkenes occurs. 

Although oxidation of homoallylic alcohols with PDC normally leads uneventfully to the desired (3,y-unsaturated carbonyl compound,164 in some cases complex mixtures are obtained.165 It is quite remarkable that oxidations of homoallylic alcohols with PDC result, only quite exceptionally, in migration of the alkene into conjugation with the resulting carbonyl compound,166 even in cases where such migration would be greatly favoured by thermodynamics.167... 

Homoallylic alcohols are oxidized, in the presence of pyridinium trifluoroacetate, with no migration of the alkene into conjugation with the carbonyl, even in cases in which such migration can occur under very mild acidic catalyses. On the other hand, the stronger acid H3PO4 is able to produce such isomerizations.14b... 

The Swern oxidation of homoallylic alcohols leads to a (3,y-unsaturated carbonyl compound, which sometimes suffers an in situ base-induced isomerization of the alkene into conjugation with the carbonyl group.239... 

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