ETHYLIDENE VINYL

Hydrosilylation of I-vinyl-1-cyclohexene (77) proceeds stereoselectively to give the (Z)-l-ethylidene-2-silylcyclohexane 78, which is converted into (Z)-2-ethylidenecyclohe.xanol (79)[74]. Hydrosilylation of cyclopentadiene affords the 3-silylated 1-cyclopentene 80. which is an allylic silane and used for further transformations[75.75a]. Cyclization of the 1,3,8, lO-undecatetraene system in the di(2.4-pentadienyl)malonate 69 via hydrosilylation gives the cyclopentane derivative 81. which corresponds to 2.6-octadienylsilanc[l8,76]. 

The reaction of vinyl acetate and stearic acid makes vinyl stearate and acetic acid but also some unwanted ethylidene acetate. A high selectivity is obtained by reaction in a distillation column with acetic acid overhead and vinyl stearate to the bottom (Geelen and Wiffels, Proc. 3d Europ. Symp. Chem. React. Eng., Pergamon, 1964, p. 125). 

The gases from the reactor are then cooled and subjected to a caustic wash to remove unreacted hydrogen chloride. This is then followed by a methanol wash to remove water introduced during the caustic wash. A final purification to remove aldehydes and ethylidene dichloride, formed during side reactions, is then carried out by low-temperature fractionation. The resulting pure vinyl chloride is then stored under nitrogen in a stainless steel tank. 

Owing to the tendency for ethylidene diacetate to be formed at elevated temperatures, care is taken for the rapid removal of vinyl acetate from the reaction vessel as soon as it is formed (Figure 14.1). 

In 1953 the Celanese Corporation of America introduced a route for the production of vinyl acetate from light petroleum gases. This involved the oxidation of butane which yields such products as acetic acid and acetone. Two derivatives of these products are acetic anhydride and acetaldehyde, which then react together to give ethylidene diacetate (Figure 14.2.)... 

Exposure of the ethylidene diacetate to an aromatic sulphonic acid in the presence of five times its weight of acetic anhydride as diluent at 136°C will yield the following mixture 40% vinyl acetate 28% acetic acid 20% acetic anhydride 4% ethylidene diacetate 8% acetaldehyde. 

One result of all these reactions is the change of the vinyl group to an ethylidene group (CHj CH. -A-CH3. CH ) with the formation of the opo-bases, e.g., opocinchonidine and 3-cinchonidine, which are the two geometrical isomerides required by the formula (E Q = quinolyl residue). 

Moiseev et al., who proposed initially that ethylidene diacetate was produced from addition of acetic acid to vinyl acetate, later showed this to be impossible from the result of reaction in CH3CO2D, preferring the following mechanism ... 

S), 15(R), and 16(S) (Scheme 19). Consequently, the problem regarding the transformation of 73 to 18 appears to involve simply the formation of the key C-7—C-20 bond from the rear side to construct rings C and E of 18 with the correct stereochemistry and the simultaneous conversion of the ethylidene side chain and the indole chromophore of 73 to the vinyl and the... 

However, the proposed in vivo transformation of anhydrovobasinediol to gelsemine might involve a series of more extensive alterations of the molecular skeleton which presumably would include (1) oxidation of the 2,7 double bond, (2) an acid-induced 2,7 shift, and (3) allylic rearrangement of the C-20 ethylidene side chain to a C-20 vinyl, so that a humantenine-type precursor... 

Another molecule which takes part in the cocyclization [see Eq. (67)] is arylisocyanate. The C=N double bond, rather than the C=0 double bond in phenylisocyanate, reacts with butadiene to give 3-ethylidene-l-phenyl-6-vinyl-2-piperidone (114) in 75% yield. In this reaction, the double bond migration to the conjugated position took place (101). With isoprene, the selective head-to-head dimerization-cyclization took place at 100°C to give 3,6-diisopropenyl-l-phenyl-2-piperidone (115). 

As these acetals could be converted into the 4,6-O-ethylidene derivatives on treatment with acid, it was reasoned that use of a cyclic vinyl ether, namely, 3,4-dihydro-2H-pyran, might prevent this second process, thus leading to a more useful method of selective acetalation.338 An equimolar reaction with methyl a-D-glu-copyranoside for 4 days in N,N-dimethylformamide led to utilization of 88% of the glycoside, and the 6-(tetrahydropyran-2-yl) ether constituted —85% of the crude reaction-product. In contrast to the steric control apparent in this instance, reaction of 3,4-dihydro-2H-pyran with the axial and equatorial hydroxyl groups in dl-1,4,5,6-tetra-O-acetyl-mi/o-inositol was completely unselective,339 a fact that has been rationalized310 in terms of the probable mechanism of these reactions. 

On the other hand, ( )-corynantheine was achieved from key intermediate 301, used previously in the synthesis of ajmaline (167). The fra/u-tosylhydrazone derivative 302 afforded the desired vinyl-substituted indolo[2,3-o]quinolizine 304 in moderate yield along with the corresponding ethylidene-substituted isomer. Formylation and methylation of 304 afforded finally ( )-corynantheine (164). 

Water also causes a change in the reaction medium, which may be advantageous. A drawback of the reducing medium in the Eastman process is that in addition to acetic anhydride, the by-product ethylidene diacetate is formed, CH3CH(AcO)2. This can be thermally decomposed to vinyl acetate and acetic acid, or it can be reduced to ethyl acetate, which in the recycle would lead eventually to propionic acid. 

Ballantyne B, Myers RC, Klonne DR Comparative acute toxicity and primary irritancy of the ethylidene and vinyl isomers of norbornene.y Appl Toxicol 17(4) 211-221, 1997... 

Starting from acetic anhydride, according to Equation 7, vinyl acetate can be obtained via ethylidene diacetate (22). 

This report describes a process to produce vinyl acetate with high selectivity from exclusively methanol, carbon monoxide, and hydrogen. The simplest scheme for this process involves esterifying acetic acid with methanol, converting the methyl acetate with syn gas directly to ethylidene diacetate and acetic acid, and finally, thermal elimination of acetic acid. Produced acetic acid is recycled. Each step proceeds in high conversion and selectivity. 

As indicated above, ethylidene diacetate (EDA) is a precursor of vinyl acetate by thermal elimination of acetic acid (equation 3). 

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