Alkene terminal

The literature states that if one uses ice cold, concentrated sulfuric acid on a terminal alkene (a.k.a. allylbenzene) an alcohol (OH) intermediate will form Markovnikoviy on the secondary carbon (don t ask). What does this mean Let s take an example. Say one has some elemi oil and wants that elemicin that is in it. What one can do is chili, say, 500mLs of the oil to freezing and do the same for about 100-200mLs of concentrated sulfuric acid (at least 90% cone.). Next, one just mixes the two together for about 5 min. What will happen is that the cold H2SO4 will make a hydrogen... 

For molecules similar to safrole or allylbenzene we take the work done on any terminal alkene such as 1-heptene, 1 octene. Another term to look for is olefin which is a term for a doublebond containing species. What we then look for are articles about these olefins where the functional groups we are looking for are formed. Articles with terminology like methyl ketones from (P2P), ketones from , amines from etc. Or when we want to see about new ways to aminate a ketone (make final product from P2P) we look for any article about ketones where amines are formed. Sound like science fiction to you Well, how do you think we came up with half the recipes in this book It works ... 

The dream of every X chemist is to get that amine function directly on the safrole molecule without having to go thru any intermediate such as the ketone of MD-P2P or the bromine of bromosafrole. But Strike can tell you right now that that is very, very tough (that is why there ain t no methods for it). About the only article Strike has ever found for the actual placement of an amine directly on a terminal alkene (a.k.a. safrole) is the following [79] ... 

This following article was sent to Strike by Osmium and Feck (are they the same person ). It involves the direct addition of azide to a terminal alkene (you-know-who) by the in situ production of the reactant mercury (II) azide from mercuric acetate and sodium azide (please don t ask) [80]. 

The oxidation of higher alkenes in organic solvents proceeds under almost neutral conditions, and hence many functional groups such as ester or lac-tone[26,56-59], sulfonate[60], aldehyde[61-63], acetal[60], MOM ether[64], car-bobenzoxy[65], /-allylic alcohol[66], bromide[67,68], tertiary amine[69], and phenylselenide[70] can be tolerated. Partial hydrolysis of THP ether[71] and silyl ethers under certain conditions was reported. Alcohols are oxidized with Pd(II)[72-74] but the oxidation is slower than the oxidation of terminal alkenes and gives no problem when alcohols are used as solvents[75,76]. 

Higher terminal alkenes are oxidized to methyl ketones and this unique oxidation of alkenes has extensive synthetic applications[23]. The terminal alkenes can be regarded as masked methyl ketones, which are stable to acids, bases, and nucleopliiles[24]. The oxidation of terminal alkenes to methyl ketones has been extensively applied to syntheses of many natural products[77]. 

The oxidation of terminal alkenes with an EWG in alcohols or ethylene glycol affords acetals of aldehydes chemoselectively. Acrylonitrile is converted into l,3-dioxolan-2-ylacetonitrile (69) in ethylene glycol and to 3,3-dimetho.xy-propionitrile (70) in methanol[28j. 3,3-Dimethoxypropionitrile (70) is produced commercially in MeOH from acrylonitrile by use of methyl nitrite (71) as a unique leoxidant of Pd(0). Methyl nitrite (71) is regenerated by the oxidation of NO with oxygen in MeOH. Methyl nitrite is a gas, which can be separated easily from water formed in the oxidation[3]. 

The alkenylpalladium intermediate 364, formed by the intramolecular insertion of 363, is terminated by hydrogenolysis with formic acid to give the terminal alkene 365[266]. The intramolecular insertion of 366 is terminated by the reaction of the alkynylstannane 367 to afford the conjugated dienyne system 368[267j. 

The dienyne 394 undergoes facile polycyclization. Since the neopentylpalla-dium 395 is formed which has no hydrogen /J to the Pd after the insertion of the disubstituted terminal alkene, the cyclopropanation takes place to form the tt-allylpalladium intermediate 396, which is terminated by elimination to form the diene 397(275]. The dienyne 398 undergoes remarkable tandem 6-e. o-dig. 5-cxo-trig. and -exo-trig cyclizations to give the tetracycle 399 exclu-sively(277]. 

The decarbonylation-dehydration of the fatty acid 887 catalyzed by PdCl2(Ph3P)2 fO.Ol mol%) was carried out by heating its mixture with acetic-anhydride at 250 C to afford the terminal alkene 888 with high selectivity and high catalyst turnover number (12 370). The reaction may proceed by the oxidative addition of Pd to the mixed anhydride[755]. 

Formic acid behaves differently. The expected octadienyl formate is not formed. The reaction of butadiene carried out in formic acid and triethylamine affords 1,7-octadiene (41) as the major product and 1,6-octadiene as a minor product[41-43], Formic acid is a hydride source. It is known that the Pd hydride formed from palladium formate attacks the substituted side of tt-allylpalladium to form the terminal alkene[44] (see Section 2.8). The reductive dimerization of isoprene in formic acid in the presence of Et3N using tri(i)-tolyl)phosphine at room temperature afforded a mixture of dimers in 87% yield, which contained 71% of the head-to-tail dimers 42a and 42b. The mixture was treated with concentrated HCl to give an easily separable chloro derivative 43. By this means, a- and d-citronellol (44 and 45) were pre-pared[45]. 

Acetoxy-l,7-octadiene (40) is converted into l,7-octadien-3-one (124) by hydrolysis and oxidation. The most useful application of this enone 124 is bisannulation to form two fused six-membered ketonesfl 13], The Michael addition of 2-methyl-1,3-cyclopentanedione (125) to 124 and asymmetric aldol condensation using (5)-phenylalanine afford the optically active diketone 126. The terminal alkene is oxidi2ed with PdCl2-CuCl2-02 to give the methyl ketone 127 in 77% yield. Finally, reduction of the double bond and aldol condensation produce the important intermediate 128 of steroid synthesis in optically pure form[114]. 

The trisannulation reagent 7-acetoxy-l,l l-dodecadien-3-one (134) is derived from the bisannulation reagent 124 in four steps. This reagent is a synthetic equivalent of l-dodecene-3,7,11-trione, and the two ketone groups of the trione are masked as an acetoxy and a terminal alkene. The synthesis of optically active D-homo-19-norandrosta-4-en-3-one (135) by the trisannulation reaction... 

The telomer obtained from the nitromethane 65 is a good building block for civetonedicarboxylic acid. The nitro group was converted into a ketone, and the terminal alkenes into carboxylic acids. The acyloin condensation of protected dimethyl dvetonedicarboxylate (141) afforded the 17-membered acyloin 142, which was modified to introduce a triple bond 143. Finally, the triple bond was reduced to give civetone (144)[120). 

Depending on the substituents of l,6-enynes, their cyclization leads to 1.2-dialkylidene derivatives (or a 1.3-diene system). For example, cyclization of the 1,6-enyne 50 affords the 1.3-diene system 51[33-35]. Furthermore, the 1.6-enyne 53, which has a terminal alkene, undergoes cyclization with a shift of vinylic hydrogen to generate the 1,3-diene system 54. The carbapenem skeleton 56 has been synthesized based on the cyclization of the functionalized 1,6-enyne 55[36], Similarly, the cyclization of the 1,7-enyne 57 gives a si -mem-bered ring 58 with the 1,3-diene system. 

Arylthiols (but not alkylthiols) add to terminal alkynes regioselectively to afford a Markovnikov-type adduct 212 in good yield using Pd(OAc)2 as a catalyst[120]. This result is clearly different from the an/i-Markovnikov addition induced by a radical initiator. The hydroselenation of terminal alkynes with benzeneselenol catalyzed by Pd(OAc)2 affords the terminal alkene 213, which undergoes partial isomerization to the internal alkene 214[121]. 

Because vicinal dihalides are prepared by addition of chlorine or bromine to alkenes (Section 6 14) alkenes especially terminal alkenes can serve as starting mate rials for the preparation of alkynes as shown m the following example... 

Hydroformylation (Section 17 5) An industrial process for prepanng aldehydes (RCH2CH2CH=0) by the reaction of terminal alkenes (RCH=CH2) with carbon monoxide Hydrogenation (Section 6 1) Addition of H2 to a multiple bond... 

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). 

Oxidation. The use of l,4-ben2oquinone in combination with paHadium(Il) chloride converts terminal alkenes such as 1-hexene to alkyl methyl ketones in high yield (81%) (32). The quinone appears to reoxidi2e the palladium. 

There are two families of conformations available to terminal alkenes. These are the eclipsed and bisected conformations shown below for propene. The eclipsed conformation is more stable by about 2kcal/mol. ... 

With more substituted terminal alkenes, additional conformations are available as indicated below for 1-butene. 

The leaving group also affects the amount of internal versus terminal alkene that is formed. The poorer the leaving group, the more El cb-like is the transition state. This trend is illustrated for the case of the 2-butyl system by the data in Table 6.6. Positively charged leaving groups, such as in dimethylsulfonium and trimethylammonium salts, may favor a more El cb-like transition state because their inductive and field effects increase the acidity of the p protons. 

The regio- and stereoselectivities of cycloadditions of trifluoroacetonitrile oxide, which is generated m situ by treatment of the tnfluoroacetohydroxamyl bromide etherate with tnethylamine in toluene (equation 31), have been determined in a senes of studies by Tanaka [55, 36, 37, 5 ]. The highly reactive nitnle oxide reacts regioselectively with a variety of activated terminal alkenes and alkynes (equations 32 and 33)... 

In a manner analogous to classic nitrile iinines, the additions of trifluoro-methylacetonitrile phenylimine occur regiospecifically with activated terminal alkenes but less selectively with alkynes [39], The nitnle imine reacts with both dimethyl fumarate and dimethyl maleate m moderate yields to give exclusively the trans product, presumably via epimenzation of the labile H at position 4 [40] (equation 42) The nitrile imine exhibits exo selectivities in its reactions with norbornene and norbornadiene, which are similar to those seen for the nitrile oxide [37], and even greater reactivity with enolates than that of the nitnle oxide [38, 41], Reactions of trifluoroacetomtrile phenyl imine with isocyanates, isothiocyanates, and carbodiimides are also reported [42]... 

Hydrogen iodide is easily eliminated by strong bases from perfluoroalky lethy 1 iodides to give terminal alkenes With perfluoroalkylpropyl iodides, however, replacement of iodine by nucleophiles predominates over the elimination reacUon [f] (equation 1)... 

Thermal decomposition of LiR eliminates a /6-hydrogen atom to give an olefin and LiH, a process of industrial importance for long-chain terminal alkenes. Alkenes can also be produced by treatment of ethers, the organometallic reacting here as a very strong base (proton acceptor) ... 

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