2- ethylidene acetal

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). 

In the following example the ethylidene acetal was used because attempts to make the acctonide led to formation of 1 1 mixture of the 1,3- and 1,4-... 

AC2O, cat. H2SO4, 20°, 5 min, 60% yield. The ethylidene acetal is cleaved to form an acetate that can be hydrolyzed with base. 

Cleavage occurs by prior conversion to the ethylidene acetal with RaNi or Bu3SnH and then the normal acid hydrolysis. The trichloro acetal is cleaved by reduction (H2, Raney Ni, 50% NaOH, EtOH, 15 min). The trichloro acetal can probably be cleaved with Zn/AcOH [cf. ROCH(R )OCH2CCl3, cleaved by Zn/AcOH, AcONa, 20°, 3 h, 90% yield. ... 

Photochemical Reactions of Benzylidene and Ethylidene Acetals of Carbohydrates... 

Summarizing, it may be concluded that the ease of hydrogenolysis is (1) cyclic orthoester > isopropylidene acetal, cyclohexylidene acetal > benzylidene acetal > ethylidene acetal > methylene acetal, and (2) 5,6-O-linked and 3,5-O-linked > 1,2-0-linked acetals. 

S. Hanessian and E. Moralioglu, Chemistry of l-(dimethylamiiio)ethylklcne and a-(dimethyl-amino)benzylidene acetals. Utility as blocking groups for diols and for selective esterification. Tetrahedron Lett. 813 (1971) S. Hanessian and E. Moralioglu, Chemistry and synthetic utility of a-(dimethylamino)benzylidene and 1 -(dimethy lamino)ethylidene acetals. Con. J. Chem. 

J. O. Buchanan and A. R Edgar, Acetoxoniuin ions from acetoxyoxiranes and ccthoesten Their conversion into ethylidene acetals, rearrangement, and solvolysis, Carbohydr. Res. 49 289 (1975). 

SCHEME 4.13 Application of the l-cyano-2-(2-iodophenyl)-ethylidene acetal for the synthesis of a fS(l- 3)-D-rhamnotetraose. CSA, 10-camphorsulfonic acid. 

In 1923, Hill and Hibbert23 published a novel method for the synthesis of ethylidene acetals this entailed treatment of the glycol with acetylene in the presence of 93 % sulfuric acid and a trace of mercuric sulfate. They postulated a mechanism for the reaction which did not involve the formation of acetaldehyde as an intermediate. 

Ethyl ethers, to protect phenols, 147 Ethylidene acetals, to protect 1,2- and... 

In a similar manner, ethylidene acetals, cyclopentylidene acetals, cyclohexylidene acetals, arylidene acetals and cyclic carbonates can be prepared. 

D. Crich and A. A. Bowers, 4,6-0-[l-Cyano-2-(2-iodophenyl)ethylidene] acetals. Improved second generation acetals for the stereoselective formation of /J-D-mannopyranosides and regioselective reductive radical fragmentation to /J-D-Rhamnopyranosides. scope and limitations, J. Org. Chem., 71(2006)3452-3463. 

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