Olefins inversion

Olefin inversion. The adduct of TeCl4 with alkenes is reduced by sodium sulfide to an olefin and tellurium. The adduct is formed predominately by cis-addition, whereas reduction involves rraiu-elimination via an epitelluride. As a consequence the overall reaction proceeds with inversion of the olefin. For example, (Z)-2-butene can be converted into an 81 19 mixture of (F> and (Z)-2-butcne. 

Olefin inversion (c/. 7, 338). Trifluoroacetyl chloride reacts with 1,2-dialkyl epoxides in DMF stereospeciflcally by trans opening to give u/c-chlorohydrin trifluoroacetates. These products are reduced stcrcospccifically by Nal to alkenes with. ryn-elimination to give inverted alkenes. Reductions with zinc arc less selective. Inversion of olefins is also possible by addition of NCS in CFjCOOH (actual reagent is trifluoroacetyl hypochlorite) followed by reduction with Nal. 

Octene-l-al, 38,62 2-Octenes, 303 2-Octylamine, 554 4-Octyne, 96 2-Octyne-l-ol, 62 4-Octyne-3-one, 96 Olefin inversion, 303-304 Olefin methathesis, 570 Orcinol dimethyl ether, 465 Orcinol monomethyl ether, 465 Osmium tetroxide, 31,575,576 Osmium tetroxide-Potassium chlorate, 361... 

Olefin inversion.2 Lithium diphenylphosphide in THF opens epoxides stereo-specifically quatemization of the crude product with methyl iodide leads to betaines, which fragment under mild conditions (25°) to give an olefin and methyldiphenyl-phosphine oxide. The product olefins are formed with inversion of stereochemistry relative to the starting epoxide owing to SN2 epoxide opening followed by cis elimination of the phosphine oxide. Thus the oxide of fraus-stilbene (1) is converted into the betaine (2), which at 25° gives cis-stilbene (3) in 95% yield overall. The conversion is stereospecific (> 98%). Similarly cis-stilbene can be converted into franx-stilbene. 

Treatment of epoxides with lithium diphenylphosphide followed by oxidation gives i3-hydroxydiphenylphosphine oxides which can be fragmented to olefins stereospecifically, thus constituting an olefin inversion (Scheme 2). 

The key intermediate should be a deuterated vinylpalladium species (H) generated via syn addition of D-Pd species (Scheme 9). This vinylpalladium intermediate H is similar in its structure to the Negishi intermediate in the Mizoroki-Heck-type cyclization of 2-iodo-1,6-dienes to six-membered carbo-cycles, which proceeds with olefmic geometry inversion[53-56]. Thus, the plausible mechanism follows a D-Pd syn addition, p-carbon elimination, and P H elimination mechanism effective in controlling olefin inversion via cyclopropane intermediate (E and then I). 

Olefin inversion. This reaction can be accomplished by conversion of the olefin into the ntc-dichloride (CI2 in CH2CI2) or nic-bromochloride (HCl-NBS in CH2CI2) followed by sodium iodide reduction in DMF as formulated (equation I). The first reaction involves rr wts-add tion, whereas the second is a... 

Olefin inversion. This inversion can be accomplished by epoxidation, reaction with triphenylphosphine dibromide or dichloride to give a ic-dihalide, and then /rans-elimination of the added halo groups with zinc-acetic acid (equation I). The sequence involves two inversions, one at each carbon joined to oxygen. ... 

Olefin inversion via epoxides is reported by two groups of workers. One sequence involves epoxidation with peracid, which occurs with retention of stereochemistry, followed by deoxygenation with hexamethyldisilane and potassium methoxide in HMPT at 65 °C. The alternative procedure utilizes reaction of the episode with triphenylphosphine dihalides to give vicinal dihalides. Zinc reduction of the dihalides is specifically trans, and thus the sequence epoxidation-bromination-reduction gives overall inversion of olefin configuration. ... 

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