Hydrolysis from alkenes

Alkenes are reduced by addition of H2 in the presence of a catalyst such as platinum or palladium to yield alkanes, a process called catalytic hydrogenation. Alkenes are also oxidized by reaction with a peroxyacid to give epoxides, which can be converted into lTans-l,2-diols by acid-catalyzed epoxide hydrolysis. The corresponding cis-l,2-diols can be made directly from alkenes by hydroxylation with 0s04. Alkenes can also be cleaved to produce carbonyl compounds by reaction with ozone, followed by reduction with zinc metal. 

OXAZOLINES FROM ALKENES, 398 OXAZOLINES FROM a-ISOCYANOESTERS, 407 OXAZOLINES FROM [4 + 2] CYCLOADDITIONS, 411 HYDROLYSIS OF OXAZOLINES, 419 21... 

A number of silyl enol ethers of acyl silanes have been produced from alkenes by subjection to 50 atmospheres of carbon monoxide in the presence of 0.1 equivalents of trialkylsilane and 2 mol% of an iridium catalyst (Scheme 26)102. Hydrolysis to the acyl silanes was achieved using hydrochloric acid-acetone. 

The Prevost Reaction allows the synthesis of anti-diols from alkenes by the addition of iodine followed by nucleophilic displacement with benzoate in the absence of water. Hydrolysis of the intermediate diester gives the desired diol.The Woodward Modification of the Prevost Reaction gives syn-diols. 

Catalysts of this type can be used not only for the enantioseleetive generation of epoxides from alkenes, but also for the hydrolytic kinetic resolution (HKR) of racemic epoxides, particularly the terminal variety. For example, the cobalt(III)salen complex 2 catalyzed the enantioseleetive hydrolysis of racemic hexene oxide 3 in the presence of 0.5 equivalents of water to provide the f/ j-enantiomer in 99% ee. Here, the inorganic ligand was found to be important for catalyst activity and selectivity, with the conventional acetate ligand giving inferior results <03TL5005>. 

Scheme 8.13. 1,2-Diol synthesis from alkenes via direct osmylation or epoxidation followed by hydrolysis.

A general procedure for the preparation of keto-aldehydes (8) from cycloalkanones and their conversion into pyridines (9) has been reported. 4 Vinylogous silyl esters (6) are readily prepared from cycloalkanones and these, by reaction with allylic Grignard reagents, followed by hydrolysis, yield alkenes of type (7). The latter compounds are converted into the keto-aldehydes (8) by Pd / -catalysed oxygenation. 

Azetidin-2-ones are more reactive than y- and <5-lactams because of ring strain. This is true for the alkaline fission to give salts of / amino carboxylic acids, as well as for the acid-catalysed hydrolysis to fi-carboxyethylammonium salts. Starting from alkenes and chlorosulfonyl isocyanate, a stereocontrolled synthesis of / -amino carboxylic acids can be realized. Ammonia and amines react with azetidin-2-ones, also with ring-opening, to produce / -amino carboxylic amides. Hence they are acylated by azetidin-2-ones ... 

Carbon-Oxygen Bond Formation. CAN is an efficient reagent for the conversion of epoxides into /3-nitrato alcohols. 1,2-cA-Diols can be prepared from alkenes by reaction with CAN/I2 followed by hydrolysis with KOH. Of particular interest is the high-yield synthesis of various a-hydroxy ketones and a-amino ketones from oxiranes and aziridines, respectively. The reactions are operated under mild conditions with the use of NBS and a catalytic amount of CAN as the reagents (eq 25). In another case, N-(silylmethyl)amides can be converted to A-(methoxymethyl)amides by CAN in methanol (eq 26). This chemistry has found application in the removal of electroauxiliaries from peptide substrates. Other CAN-mediated C-0 bondforming reactions include the oxidative rearrangement of aryl cyclobutanes and oxetanes, the conversion of allylic and tertiary benzylic alcohols into their corresponding ethers, and the alkoxylation of cephem sulfoxides at the position a to the ester moiety. 

The serendipitous event that inspired the development of NPGs (see Sect. 2.1) was the attempt to prepare a bromohydrin from alkene 4 (Scheme 1) [6, 19]. With the benefit of hindsight, we now realize that this objective was predestined to fail, because the first-formed cyclic bromonium ion, e.g., 15 (Scheme 4), would undergo facile R05 interaction [26] to give a furanylium ion, 16, and thence the oxocarbe-nium ion 17. The latter would be scavenged by water to give 18 (R =H), the product of oxidative hydrolysis. 

Study of the Pd(0Ac)2/DMS0/02 system by van Benthem and co-workers t i f has opened a route to oxazolidine derivatives from alkenes bearing A-Boc-protected amino alcohols (Scheme 16). The oxazolidines obtained can readily be converted into A-Boc-protected /3-amino alcohols through anodic oxidation and hydrolysis. 

Linear Alkenes and Alkynes.— Nucleophilic addition to co-ordinated alkenes can either occur on the same side as the metal (cm attack) or on the side remote from the metal (trans attack) (Scheme 3). A study on the oxidative hydrolysis of alkenes in the... 

Electrophilic addition of bromodimethylsulphonium bromide to alkenes gives, after dehydrobromination, variable yields of vinylsulphonium salts. Hydrolysis of the vinyl thioether derivatives gives a formal conversion of an alkene into a carbonyl compound with some degree of control over regioselect-ivity. Halohydrins (derived from alkenes) can be converted into ketones by dehydrohalogenation with potassium carbonate, catalysed by palladous acetate. ... 

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