Ketene Acetals. XIX. 2-Methylene-1,3-dioxolanes and 1,3-Dioxanes

McElvain, S. M.; Curry, Michael J.

doi:10.1021/ja01191a071

Cited by 121 publications

(37 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Similar treatment of a-bromo-iso-valeraldehyde ethyleneacetal provided primarily the ketene acetal, but in this case the a,gunsaturated acetal was also formed, though only to the extent of 14% of the product (experiment 7, Table 1). These results are contrary to those expected on the basis of the previous work (1)(2)(3)(4). Accordingly, the dehydrohalogenation of several homologues of these a-bromoaldehyde ethyleneacetals (experiments 1, 2, 4, 8, 11) and of the acetal obtained from a-bromo-n-valeraldehyde and 1,3-propanediol (experiment 12) was investigated.…”

Section: Resultscontrasting

confidence: 65%

“…It is seen that base-catalyzed dehydrohalogenation of our 2-(a-bromoalky1)-l,3-dioxolanes (the ethyleneacetals) and of 2-(a-bromoalky1)-l,3-dioxane generally provides the ketene acetal in greater proportion, and in several cases exclusively (experiments [1][2][3][4]7,8,12). The only one which does not follow this general course is the tetramethylated 1,3-dioxolane of experiment 1 1, and this goes to the other extreme in giving only the a,P-unsaturated, acetal.…”

Section: Resultsmentioning

confidence: 99%

“…They found that base-catalyzed For a part of our general study of the hydrogenolysis of acetals and ketals, several a,Punsaturated ethyleneacetals were required. The preparation of a few a,P-unsaturated dialkylacetals has been described by McElvain et al pare some a-bromo acetals from diols, but none of these had an alkyl group attached to the a carbon, hence on dehydrohalogenation these could produce only the ketene acetals (4). This paper describes the results of our experiments concerning the base-catalyzed dehydrobromination of several a-bromoacetals derived from the combination of some higher homologues of a-bromoacetaldehyde with dihydroxy alcohols as well as with some monohydroxy alcohols.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Base-catalyzed Dehydrobromination of Several α-Bromoacetals

Davis¹,

Brown²

1971

Can. J. Chem.

View full text Add to dashboard Cite

Base-catalyzed dehydrohalogenation with potassium t-butoxide in t-butyl alcohol of the acetals obtained from homologues of a-bromoacetaldehyde and ethylene glycol[2-(a-bromoalky1)-l,3-dioxolanes] or 1,3-propanediol[2-(a-bromoalky1)-l,3-dioxane] provides the corresponding ketene acetal, in some cases exclusively and in others as the major product along with a smaller proportion of the a,b-unsaturated acetal. In contrast, similar dehydrohalogenation conditions convert the acetals obtained from homologues of a-bromoacetaldehyde and monohydroxy alcohols, to the a#-unsaturated acetals, in some cases exclusively, and in others as the major product accompanied by a smaller proportion of the corresponding ketene acetal.The preference for the ketene acetal formation from the 2-(a-bromoalky1)-l,3-dioxolanes (the ethylene acetals) is believed due to greater ease of approach by base to the methine proton as a result of the restricted shape of the 1,3-dioxolane ring. Approach by base to the methine proton of the a-bromoalkyl dialkylacetals is more hindered by the two alkoxy groups, which cause preferred attack by base at the proton to provide the a,a-unsaturated acetal.The proportion of a,a-unsaturated acetal obtained from base-catalyzed dehydrohalogenation of 2-(a-bromoalky1)-l,3-dioxolanes can be greatly increased if the reaction is carried out in dimethyl sulfoxide. This marked change in proportion of products is thought to be due to a change in mechanism occasioned by the dimethyl sulfoxide.La dChydrohalog6nation baso-catalys8e avec le t-butoxyde de potassium dam I'alcool t-butylique, La formation prkfkrentielle de IYac6tal ckt8ne a partir des (a-bromoalky1)-2 dioxolanes-1,3 (les BthyIkneac6tals) est probablement due a une plus grande facilite d'approche du proton methyne par la base et ceci probablement par suite de la forme restreinte du cycle du dioxolane-1,3. L'approche par une base du proton methyne des a-bromoalkyl dialkylac6tals est plus empikhk par les deux groupes alkoxy qui provoquent I'attaque preferentielle par une base sur le proton ! 3 pour conduire a un adtal a-a insatur6.Le proportion d'ac6tal a-!3 insaturC obtenu par d6hydrohalogenation baso-catalysk des (a-bromoa1kyl)-2 dioxolanes-1,3 peut &tre de beaucoup augmentee si la reaction est effectu6e dans le dimethyl sulfoxyde. Cette modification importante dam la proportion des produits obtenus est probablement due a un mecanisme different provoque par le dimethyl sulfoxyde. Canadian Journal of Chemistry, 49,2321 (1971)Introduction ketene acetals. They found that base-catalyzed For a part of our general study of the hydrogenolysis of acetals and ketals, several a,Punsaturated ethyleneacetals were required. The preparation of a few a,P-unsaturated dialkylacetals has been described by McElvain et al. dehydrohalogenatioi of a-haloacetals contaLing only hydrogen, aryl, or halogen substituents on the a carbon, gave only ketene acetals (1 in eq. a, Scheme 1). However, if the a carbon had attached to it a carbon atom bearing one or more hydrogen atoms, then only th...

show abstract

Section: Resultscontrasting

confidence: 65%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Base-catalyzed Dehydrobromination of Several α-Bromoacetals

Davis¹,

Brown²

1971

Can. J. Chem.

View full text Add to dashboard Cite

show abstract

“…The dehydrohalogenation of halomethyl compounds, a basic elimination technique, is one of the most common reactions proven to be a suitable method for many different monomers, especially exo-methylene moieties in all positions of simple 5-, 6-and 7-membered systems [133]. Beside some unusual special methods the elimination of HX from cyclic halomethyl acetals or b-halomethyl ethers by potassium tert-butoxide as well as alcohol cleavage from orthoesters catalyzed by aluminum tert-butoxide are widely used and well established in the synthetic praxis [134,135]. Some more reactions use sodium methylate [90] as steric less hindered base or bulky 1.8-diazabicyclo-[5.4.0]-undecene-(7) (DBU) [102].…”

Section: Synthetic Aspectsmentioning

confidence: 99%

Ring-opening polymerization of heterocycles bearing substituted and unsubstituted exo-methylene groups - a review

Klemm

Schulze

1999

Acta Polym.

View full text Add to dashboard Cite

Monocyclic monomers bearing exo‐methylene groups are likely to undergo ring‐opening polymerization under the conditions of radical or cationic initiation. Several structural features will determine the course of reaction after initiation by species that exclusively attack the exo‐methylene functionality. Reviewing some of the most common classes of monocyclic heterocycles it becomes obvious that a monomer has to meet certain structural preconditions that makes them suitable for isomerizations. Among the considered heterocycles there are some types of monomers possessing an outstanding ring‐opening behavior following polymerization mechanisms free from side‐reactions. The combination of strain release due to ring‐opening isomerization, an energy decrease in the transition state caused by the formation of carbonyl‐functionalities and an appropriate stabilization of the growing chain end by steric and electronic effects may lead to clear ring‐opening mechanisms. However, this property remains restricted to only some special monomers with simple aromatic substituents being attached to the cycle. Hence a variety of cyclic ketene acetals, enolethers, (meth)acrylates, carbonates, lactones and lactames have been chosen in order to demonstrate both the possibilities and limits of ring‐opening.

show abstract

“…:C52,14,H7,32,N13, (3)); 7,54 (s. NH (1)). "C-NMR (62,89 MHz, CDCI,): 16.0 (-, d, 'J(P,C) = 7,6,CH,CH,Oj;35,9 (+,d,'J(P,Cj = 225,') C=C (2) (2)). MS: 245 (24,M+j,84 (100,C,H,N:j. Anal.…”

mentioning

confidence: 99%