content_image/924008.jpg content_image/924012.jpg content_image/924010.jpg content_image/924009.jpg
[0095] In this instance, b can be an optionally substituted nitrogen and a and c can be oxygen, nitrogen or carbon, it being possible for the two latter atoms to carry a hydrocar› bon radical or a hydrogen. 

[0096] For this type of reaction, reference is made to the general work Advanced Organic Chemistry, third edition, by Jerry March, page 743 et seq., and to the documents cited in this reference work. 

[0097] The heating of these compounds gives cycloaddi› tion in the presence or absence of a solvent, even without catalyst. However, some of the compounds with a canonical form which has been mentioned above have to be synthe› sized in situ. 

[0098] The following nonlimiting examples illustrate the invention. 

[0099] In this instance, Rfis trifluoromethyl, R$_{1 }$ and R$_{3 }$ are hydrogen and S is chlorine. 

<img src='content_image/924008.jpg'>

[0100] The reaction equation is given above with some of the impurities identified. 

<img src='content_image/924012.jpg'>

(a) $^{19}$F NMR with internal standard; 

(bladdition at 0° C. and then left to react at a.t.; 

(c)addition at 0° C., left in the ice bath for ‰ hour and then left to react at a.t.; 

(d)(16) and (21) could not be separated by $^{19}$F NMR: (16) + (21) - 12.3% 

## Dehydrohalogenation of the Precursor CF $_{3}$CH$_{2}$CHClCH$_{2}$OAc 

## EXAMPLE 1 

## Dehydrohalogenation of the Precursor CF$_{3}$ CH$_{2}$CHC1CH$_{2}$Oac in the Presence of DMF 

[0101] 

<img src='content_image/924010.jpg'>

(2): 1830 g [8.95 mol] DBU: 1500 g [9.85 mol] DMF: 7.5 liters 25° C., 2 to 3 hours 80% 

## Dehydrohalogenation of the Precursor CF$_{3}$CH$_{2}$ CHC1CH$_{2}$ OAc Using Potassium Carbonate 

[0102] It was demonstrated that potassium carbonate makes it possible to carry out this dehydrochlorination reaction no longer at 25° C. but at 60° C. and in dipolar aprotic solvents, such as DMF or NMP (DN=27.3): 

<img src='content_image/924009.jpg'>

## EXAMPLE 2 

## EXAMPLE 3 

