Acetylenes and Olefins

Intermolecular olefin and acetylene insertion into zirconaaziridines has been studied by Buchwald and coworkers. High regio- and diastereoselectivity is observed for the formation of the 3,4-disubstituted product 23 in Eq. 10 [20]. Only a single diastereomer of the resulting chiral amine is isolated upon acidic workup. 

The eventual product of such reactions (after cleavage of the Zr-C bond during workup [51]) is an amine with a vinyl or alkyl substituent (arising from the alkyne or alkene) at the a position. Whitby thus derivatized tetrahydro-quinoline, following in situ generation of the zirconaaziridine 26, by alkyne, alkene, or allene insertion (Eq. 11) [52,53]. 

JV-heterocycles can be prepared by inserting olefins or acetylenes with pendant electrophiles. Typical electrophiles used are alkyl halides and epoxides. The latter do not react with the zirconaaziridine, but with the amine generated 

Similarly, the regio- and diastereoselective formation of azetidines can be accomplished through olefin insertion into the Zr-C bond of zirconaaziridines (Eq. 14). Cleavage of the Zr-C bond with I2 introduces an alkyl iodide functionality, which alkylates at nitrogen to result in intramolecular cyclization and the diastereoselective formation of azetidines, the products of the formal zirconium-mediated [2+2] reaction of an imine and an olefin. Hindered cyclic alkenes can also insert into the Zr-C bonds of zirconaaziridines to yield bi-cyclic products [55], albeit with low diastereoselectivity (2 1 for norbornene). 

Asymmetric versions of these transformations can be carried out when resolved EBTHI zirconaaziridines are used (Eq. 15). The allylic amine products (Table 3) resulting from alkyne insertion followed by workup are not only geometrically pure, but also enantiomerically enriched the ee is high for a variety of substrates [18]. A phenyl substituent (R1) on the zirconaaziridine 

The reaction is insensitive to steric effects, but kj increases with the number of alkyl substituents although it is not influenced by position of the alkyl groups (unlike oxidation by TI(III)) . In these respects Cr(VI) oxidation resembles bromination, chlorination and epoxidation and a symmetrical transition state of the type depicted is favoured. 

Chromyl chloride oxidation of alkenes proceeds via the formation of adducts at a rate necessitating stopped-flow techniques. At 15 °C the formation of 1 1 adduct from styrene and oxidant in CCI4 solution is simple second-order with 2 = 37.0 l.mole .sec . Measurements with substituted styrenes yielded = — 1.99. E = 9.0 kcal.mole and = —23.8eu for styrene itself. Hydrolysis of the styrene adduct yields mostly phenylacetaldehyde (76.5 %)and benzaldehyde (21.1 %). Essentially similar results were obtained with a set of 15 alkenes and 

Thus d[Mn04 ]/dt = —A j[Mn04 ][crotonate] —/cjLMnO ][B] and d[B]/d/= l[Mn04 ][crotonate] —A 2[Mn04 ][B]. Elimination of time as a variable followed by integration and further manipulation leads to an expression for k.  

At pH 13 the final products are manganate and cw-diol. The observation of a large degree of transfer of 0 from labelled MnO into oleate ion at pH 12 suggests formation of a cyclic ester, viz. 

The oxidation of a series of olefins reveals the reaction to be very insensitive to electronic effects . Phenyl and methyl substitution of the olefin mildly accelerate reaction. In all cases A , is pH-independent. Data are collected in Table 1. 

As discussed in detail below (Section 3.2), compounds containing an olefinic bond, ranging from compounds as simple as ethylene to more complex structures such as allylisopropylacetamide (AIA), 

Terminal acetylenes, like terminal olefins, alkylate the P450 prosthetic heme (see Section 

but compounds such as 10-undecynoic acid, 1-ethynylpyrene, 17p-ethynylprogesterone, 17a-ethynylestradiol (EE), and 9- and 2-ethynyl-naphthalene have been shown to inactivate P450s primarily by binding covalently to the protein with only partial loss of the heme group  

In contrast, CYP2B1-catalyzed addition of the activated oxygen to the internal rather than terminal triple bond carbon of phenylacetylene results in heme X-alkylation rather than protein acylation (see below) Predominant inactivation of CYP2B1 by phenylacetylene via heme alkylationand by 2-ethynylnaphthalene via protein acylation sheds some light on the influence exerted by the fit of the inhibitor within the active 

Peptide mapping and amino acid sequence analysis of radiolabeled peptides indicate that 

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The high acidity of superacids makes them extremely effective pro-tonating agents and catalysts. They also can activate a wide variety of extremely weakly basic compounds (nucleophiles) that previously could not be considered reactive in any practical way. Superacids such as fluoroantimonic or magic acid are capable of protonating not only TT-donor systems (aromatics, olefins, and acetylenes) but also what are called (T-donors, such as saturated hydrocarbons, including methane (CH4), the simplest parent saturated hydrocarbon. 

Olefin and acetylene complexes of Au(I) can be prepared by direct iateraction of the unsaturated compounds with a Au(I) hahde (190,191). The resulting products, however, are not very stable and decompose at low temperatures. Reaction with Au(III) hahdes leads to halogenation of the unsaturated compound and formation of Au(I) complexes or polynuclear complexes with gold ia mixed oxidatioa states. 

In general, hydroboration—protonolysis is a stereoselective noncatalytic method of cis-hydrogenation providing access to alkanes, alkenes, dienes, and enynes from olefinic and acetylenic precursors (108,212). Procedures for the protonolysis of alkenylboranes containing acid-sensitive functional groups under neutral or basic conditions have been developed (213,214). 

CsH5)2Ti [1271-29-0] Ti(II) Cpj dark green 200 pyrophoric catalyst for polymeti-zation of olefins and acetylenes... 

Carbometalation of olefins and acetylenes is a useful reaction. For example, in... 

Protonated /V-chloroalkyl amines under the influence of heat or uv light rearrange to piperidines or pyrroHdines (Hofmann-Lriffler reaction) (88). The free-radical addition of alkyl and dialkyl-/V-chloramines to olefins and acetylenes yields P-chloroalkji-, P-chloroalkenyl-, and 8-chloroalkenylamines (89). Various N-hiomo- and N-chloropolyfluoroaLkylarnines have been synthesized whose addition products to olefinic double bonds can be photolyzed to fluoroazaalkenes (90). 

Methyl ketones are important intermediates for the synthesis of methyl alkyl carbinols, annulation reagents, and cyclic compounds. A common synthetic method for the preparation of methyl ketones is the alkylation of acetone derivatives, but the method suffers limitations such as low yields and lack of regioselectivity. Preparation of methyl ketones from olefins and acetylenes using mercury compounds is a better method. For example, hydration of terminal acetylenes using HgSO gives methyl ketones cleanly. Oxymercuration of 1-olefins and subsequent oxidation with chromic oxide is... 

A very significant recent development in the field of catalytic hydrogenation has been the discovery that certain transition metal coordination complexes catalyze the hydrogenation of olefinic and acetylenic bonds in homogeneous solution.Of these catalysts tris-(triphenylphosphine)-chloror-hodium (131) has been studied most extensively.The mechanism of the deuteration of olefins with this catalyst is indicated by the following scheme (131 -> 135) ... 

Perfluoroalkylation of olefins and acetylenes occurs in low yields when perfluoroalkylcopper reagents are heated with alkenes or acetylenes in DMSO [226, 237, 238, 239]. Undine derivatives react similarly [240]... 

Selenium diimides react in a manner similar to SeOa with unsaturated organic compounds. The first report of BuN=Sc=N Bu described its use as an in situ reagent for allylic amination of olefins and acetylenes. Improved procedures for this process (Eq. 10.5) and for the diamination of 1,3-dienes (Eq. 10.6) have been developed using the reagents RN=Se=NR [R = para-toluenesulfonyl (Ts), ort/io-nitrobenzenesulfonyl (Ns)]. ... 

Al-Heterocycles, formation from olefins and acetylenes in a metallocomplex-catalyzed cycloaddition reaction and further transformations 98IZV816. 

In benzene or similar solvents, tris(triphenylphosphine)halogenorhodium(I) complexes, RhX[P(C6H5)3]3, are extremely efficient catalysts for the homogeneous hydrogenation of nonconjugated olefins and acetylenes at ambient temperature and pressures of 1 atmosphere (6). Functional groups (keto-, nitro-, ester, and so on) are not reduced under these conditions. 

Mn2(CO)io is only active in the presence of acetylene derivatives, where as Re2(CO)io is active in the presence of both olefinic and acetylene derivatives. 

TABLE 13. Annelation of olefins and acetylenes with tetrachlorothiophene 1,1-dioxide116... 

A plethora of reactions has been reported for the in situ generated (OC)5W=PPh, many of which have been the topic of previous reviews [2-4]. A typical account of the versatility of this reagent with olefinic and acetylenic bonds is visuaHzed in the wagon wheel . Only a brief account with selected ex-... 

Volume 1, Metal Complexes. Describes the organopalladium complexes containing Pd—C a bonds, hydrides, olefins and acetylenes, dienes, w-allylic groups, cyclopentadienyls, and benzenes. 

Mono-olefin and acetylene complexes of nickel, palladium and platinum... 

B. Reactions.—This year has seen the publication of a number of papers on the reactions of olefins and acetylenes with phosphorus pentachloride, to produce new phosphorus-carbon bonds. An investigation into the structural requirements of trisubstituted olefins (40) undergoing the above reaction has shown that both steric and electronic factors are important, e.g. an adduct forms with (40 X = CH3) but no reaction occurs for (40 X = Ph). Further examples of the reactions of unsaturated ethers include the formation and decomposition of adducts from a-methoxystyrene... 

Tetrazolium ylides are quite reactive and are easily alkylated.168 The mesoionic tetrazolium thiolate 117 readily adds bromine to yield 174 which can then react with a number of active methylene compounds to give mesoionic compounds, e.g., 175.293,294 They also undergo 1,3-dipolar cycloaddition with olefins and acetylenes to yield bicyclic tetrazolo-thiazolines... 

The chemical consequences of these MO changes is to activate the antiaromatic diene system for reaction. This activation is especially evident in Diels-Alder cyclizations, either with itself (Eq. 32) or with a variety of olefins and acetylenes.93... 

Also, cocyclizations of butadiene with olefins and acetylenes are possible to form the 10-membered rings 7 and 8 (10) ... 

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