Ethyli dene-

The main emphasis has been on the homologation of methanol to ethanol (O. Homologation of substrates other than methanol has up till now been less widely studied. However, there is an increasing interest in the hydrocarbonylation of esters, as is evidenced by e.g. the development of the Halcon process (2 ) for the production of ethyli-dene diacetate as a precursor for vinyl acetate. 

For both reactions a RhCl3/CH3l/TPO catalyst in acetic acid as reaction solvent affords propionic acid in more than 80 % yield according to the respective stoichiometries of Equations 12 and 13. Although acetic acid is present in excess in the reaction medium, it does not participate in the homologation as reactant. Only traces of propionic acid are produced in the absence of methyl acetate, ethyli-dene diacetate or acetic anhydride under our reaction conditions. Homologation of carboxylic acids has been reported by Knifton (10) to require more severe reaction conditions (220 °C, > 100 bar). 

Z> nets was prepared from the reaction of /V, /V -bis 1 -(pyrazine-2-yl)ethyli-dene]benzildihydrazone (22) with AgNO,.64 Another type of (10,3) topology is... 

Ethylidene Diethyl Ether, See Acetal A13-L Ethylidene Oxide. See Acetaldehyde A14-L Ethyli dene-(2,4,6-trinitrophenylhy drazine). 

Synonyms Chlorinated hydrochloric ether Ethyli-dene chloride Ethylidine dichloride Chemical/Pharmaceutical/Other Class Chlorinated hydrocarbon Chemical Structure ... 

The sequence of intermediates after (26) is still an open question. Evidence has been obtained that the ethyl group of (28) is not generated directly by reduction of the vinyl group, but that the double bond first migrates to generate an ethyli-dene group.15 Thus, when [2,2-3H2,2-14C]geraniol was administered to the plant the tritium was found to be completely lost in the alkaloids (28) and (29). 

With paraldehyde and sulfuric acid at room temperature, methyl 4,6-0-ethylidene-a-D-mannopju anoside (32%) and methyl 2,3 4,6-di-0-ethyli-dene-a-D-mannopyranoside (55%) were isolated. The corresponding (8-d anomers have also been prepared. Assuming that the CA conformation is the most probable, the 4,6-acetals of methyl mannopyranosides are readily available model compounds for comparing the reactivities of equatorial (C-3) and axial (C-2) hydroxyl groups in the pyranoid ring. 

Compounds of the first class are usually prepared by the action of the halides of phosphorus on aldehydes or ketones. Ethyli-dene chloride (1,1-dichloroethane) is prepared from aldehyde inthisway -... 

Oxidative cleavage of arylmethylene acetals offers another method for the transformation of an arylmethylene acetal to a mono-protected diol. For example, benzylidene acetals of 1,2- and 1,3-diols undergo ozonolytic cleavage rapidly at -78 °C at rates that compete with cleavage of alkenes to give a benzoate ester [Scheme 3.71]. The reaction is not restricted to benzylidene acetals since ethyli-dene and /erf-butylmethylidene acetals also cleave rapidly. The reaction was creatively exploited by Stork and Rychnovsky in the closing stages of their synthesis of dihydroerythronolide A when it was used to unmask a 1,2-diol protected as a 2-methyl-l,3-dioxolane in the presence of a 2-methyl-l,3-dioxane. It is noteworthy that a 1,3-dioxane function cleaved very much slower [Scheme 3.72). 

Treatment of L-sorbose with 1,1-dimethoxyethane and a trace of p-toluenesulfonlc acid yields a wide variety of mono- and di-ethyli-dene acetals. The main products in the early stages of the reaction are 25 and 26, whereas 27 may be obtained after longer intervals. 

Benzyl, 1,2-O-ethylidene, 4,6-di-Ac 4,6-Di-O-acetyl-3-O-benzyl-l, 2-O-ethyli-dene-a-D-allopyranose [56632-48-5]... 

O-Isopropylidene, 4,6-O-ethylidene, 3-benzoyl 3-0-Benzoyl-4,6-O-ethyli-dene-l,2-0-isopropylidene-a-D-gulopyra-nose... 

O-Ethylidene Methyl 3,4-O-ethyli-dene-p-L-arabinopyranoside CgHnO, 190.196... 

O-Ethylidene Methyl 4,6-O-ethyli-dene-a-D-galactopyranoside C9H16O6 220.222... 

A number of phytosterols contain a two-carbon side chain (ethyl or ethylidene) attached to C-24, the atom which is methylated in the formation of ergosterol. The scheme of Castle et al., reproduced partially in Fig. 2, was originally proposed to account for the formation of such compounds. It was postulated that the 24-methylene compound (structure IV) might be further methylated to yield the 24-ethyl or ethylidene compounds. Evidence in favor of such double methylations has been supplied by the findings that (1) the label from [methyl- C] methionine is incorporated equally into both carbon atoms C-28 and C-29 (Castle et al., 1963 Bader et al., 1964 Villanueva et al., 1964), and (2) 24-ethyli-dene compounds may be converted to the 24-ethyl compounds by whole Pinus pinea seed (van Aller et al., 1969). That the details of the reactions may differ is indicated by deuterium labeling patterns. In some cases, only four hydrogen atoms derived from methionine are incorporated... 

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