Preparation from olefins

Following Uskokovic s seminal quinine synthesis [40], Jacobsen has very recently reported the first catalytic asymmetric synthesis of quinine and quinidine. The stereospecific construction of the bicyclic framework, introducing the relative and absolute stereochemistry at the Cg- and expositions, was achieved by way of the enantiomerically enriched trans epoxide 87, prepared from olefin 86 by SAD (AD-mix (3) and subsequent one-pot cyclization of the corresponding diol [2b], The key intramolecular SN2 reaction between the Ni- and the Cg-positions was accomplished by removal of the benzyl carbamate with Et2AlCl/thioanisole and subsequent thermal cyclization to give the desired quinudidine skeleton (Scheme 8.22) [41],... 

The reaction itself is rather attractive and useful as a synthetic tool, because of its practical simplicity. Indeed, 1,5-dicarbonyl compounds can be readily prepared from olefin and 1,3-dicarbonyl compound in a one-pot reaction. Subsequent aldolization of the resulting 1,5-dicarbonyl compounds would furnish cyclohexenones. The reaction mechanism and stereochemistry of the de Mayo reaction has been comprehensively reviewed7), and the basic strategy of which has also been developed and extended. The following examples would demonstrate some applications and variations of the de Mayo reaction. 

Alkylboranes can be coupled by treatment with silver nitrate and base.396 Since alkylboranes are easily prepared from olefins (5-12), this is essentially a way of coupling and reducing olefins in fact, olefins can be hydroborated and coupled in the same flask. For symmetrical coupling (R = R ) yields range from 60 to 80% for terminal olefins and from 35 to 50% for internal ones. Unsymmetrical coupling has also been carried out,397 but with lower yields. Arylboranes react similarly, yielding biaryls.398 The mechanism is probably of the free-radical type. 

Carboxylic esters are produced by the addition of carboxylic acids to olefins, a reaction that is usually acid-catalyzed (by proton or Lewis acids182) and similar in mechanism to 5-4. Since Markovnikov s rule is followed, hard-to-get esters of tertiary alcohols can be prepared from olefins of the form R2C=CHR.183 When a carboxylic acid that contains a double bond in the chain is treated with a strong acid, the addition occurs internally and the product is a y- and/or a 8-lactone, regardless of the original position of the double bond in the chain, since strong acids catalyze double bond shifts (2-2).184 The double bond always migrates to a position favorable for the reaction, whether this has to be toward or away from the carboxyl group. Carboxylic esters have also been prepared by the acyloxymercuration-demercuration of olefins (similar to the procedures mentioned in 5-2 and 5-4).185... 

Trialkylboranes (which can be prepared from olefins by 5-12) react with carbon monoxide314 at 100 to 125°C in the presence of ethylene glycol to give the 2-bora-l,3-dioxolanes72, which... 

Similar stereochemical results have been obtained with different starting olefins and with the aliphatic palladium compound, "carbo-methoxypalladium acetate prepared in situ from carbomethoxymercuric acetate 27> and palladium acetate 24>. The latter reagent allows unsaturated esters to be prepared from olefins. 

Electrophilic Addition.—rrans-Diequatorial diols are not readily prepared from olefins in the steroid series. The ring-opening of epoxides generally gives trans-diaxial products, whereas acyloxonium ions (65), formed during the Prevost... 

Conjugated olefinic acids containing more than one double bond are prepared from olefinic aldehydes. Thus, acrolein and crotonaldehyde with malonic acid yield vinylacrylic acid (60%) and sorbic acid, (32%) respectively. In this manner, the completely conjugated 2,4,6,8,10,12-tetradecahexaenoic acid, CH3(CH = CH)6COjH, has been made. ... 

Organo -Ca, -Sr and -Ba derivatives are prepared from the metals. With Be, however, the compounds are produced from anhydr BeCl2 and organomagnesium-halide reagents or lithium alkyls. In principle, RBe derivatives can also be formed from Be metal. Thus, a Be mirror disappears by the effect of alkyl radicals, but such reactions cannot be used in practice. Beryllium dialkyls also can be prepared from olefins and Hj with the metal in the presence of small amounts of Br2 or I2, and by the electrolysis of M[A1R3R ] complexes (M = Na, K R = alkyl R = alkyl, alkoxy) using anodes of pure Be. However, laboratory application is limited owing to the lack of detailed information and the need for expensive apparatus. 

Epoxides are usually prepared from olefins and peroxy acids (especially peroxybenzoic acid) according to the following general procedure The olefin is dissolved in chloroform, cooled, and treated with a slight excess of peroxy add in cold chloroform. The reaction mixture is set aside at 0°, or for less reactive olefins at room temperature. The course of the reaction is followed by titration of small samples when the reaction is ended, unchanged peroxy acid and the carboxylic acid formed are carefully extracted, and the chloroform solution is worked up. 

Perfluoroalkylacetylenes 4 are prepared from olefins 2 (Rp = perfluoroalkyl) by exhaustive chlorination under ultraviolet irradiation, followed by treatment with zinc. The resulting acetylenic zinc compounds 3 are decomposed by dilute hydrochloric acid. 1,1-Dibromoalk-l-enes 5 (R = Me, cyclohexyl etc. R = H or Ph) are converted into the rearranged acetylenes 7 by the action of samarium(II) iodide in benzene containing 10% HMPA alkylidenecarbenes 6 are presumed to be intermediates in this process. ... 

In order to measure the nitrogen adsorption, samples prepared from olefins were treated in vacuum at the operating temperatures until a constant weight was obtained ( coke ). On the other hand, samples resulting from isopentane... 

The use of molybdenum compounds in organic synthesis has attracted greater attention. Thus, molybdenum hexacarbonyl has been used in various reactions, such as the preparation of disulfides from sulfonyl chlorides, the alkylation of aryl derivatives, and the synthesis of 4-quinazolones from amines Oxygen has been replaced by fluorine with molybdenum hexafluoride. Molybdenum pentachloride in combination with hydroperoxides has served as oxidant Chelates of MoOg " have been investigated as catalysts for oxidations with molecular oxygen 2,2-Dichloro-7-butyrolactones have been prepared from olefins and methyl trichloracetate with cyclopentadienylmolyb-denum tricarbonyl dimer as catalyst ... 

D-Glucose orthoesters of complex alcohols can be easily obtained with the help of silver salicylate Alcohols and amines can be conveniently prepared from olefins by ozonization-reduction and ozoni-zation-reductive amination respectively without isolation of intermediates Inverted amines can be obtained from optically-active alcohols through stereospecific formation of N-alkylphthalimides 3-Methoxy-l-phenyl-l-propyne has been used as starting material for the synthesis of a,/ -unsatd. carbonyl compounds through allenic di-carbanions a-Ketocarboxylic acids can be easily prepared from cyanohydrins through a Ritter reaction... 

Acetamido selenides, easily prepared from olefins, undergo regioselective oxidative elimination to give high yields of allylic amides e.g. Scheme 54). ... 

---