Tamayo, M. Lora et al. published their research in Anales de la Real Sociedad Espanola de Fisica y Quimica, Serie A: Fisica in 1952 | CAS: 51488-33-6

3,4-Dimethoxybenzimidamide hydrochloride (cas: 51488-33-6) belongs to ethers. The oxygen atom in ethers are more electronegative than carbon, thus the hydrogens which are alpha to the ethers are more acidic than the simple hydrocarbons. Ethers are good solvents partly because they are not very reactive. Most ethers can be cleaved, however, by hydrobromic acid (HBr) to give alkyl bromides or by hydroiodic acid (HI) to give alkyl iodides.Reference of 51488-33-6

Conjugation of a double bond with an aromatic nucleus. XXVI. The amidines in the Diels-Alder reaction was written by Tamayo, M. Lora;Martinez, J. Royo. And the article was included in Anales de la Real Sociedad Espanola de Fisica y Quimica, Serie A: Fisica in 1952.Reference of 51488-33-6 This article mentions the following:

Substituted amidine HCl salts containing the conjugated diene system C:C.C:N, the C:C being a part of the aromatic nucleus, are treated with various dienophiles, such as maleic anhydride and anethole, in HOCH2CN. The substituted groups OMe, -OCH2O-, and NO2 and RC(:NH)NH2. HCl where R = CH2:CH, 3,4-CH2O2C6H3, 3,4-(MeO)2-C6H3, and m-O2NC6H4, are studied. In none of the attempted condensations does a 1,4-addition occur. In some cases a very small quantity of resinous material is found along with the unaltered amidines when no hydroquinone is used. A number of new compounds prepared are CH2:CHC(OEt):-NH.HCl m. 104-4.5°; CH2:CHC(:NH)NH2.HCl; 3,4-CH2O2C6H3C(OEt):NH.HCl, m. 122-3°, and 3,4-CH2O2-C6H3C(:NH)NH2 picrate, m. 257°. The method of preparation for the new compounds is a general one in which the nitrile is treated in absolute alc. with HCl, the imino ester formed is treated in alc. with NH3, and the corresponding amidine liberated. The picrate is prepared by treating the 3,4-CH2O2C6H3C(:NH)NH2.HCl with 20% NaOH, separating the white crystalline precipitate, adding it to a saturated alc. solution of picric acid, and recrystallizing the picrate derivative from H2O. In the experiment, the researchers used many compounds, for example, 3,4-Dimethoxybenzimidamide hydrochloride (cas: 51488-33-6Reference of 51488-33-6).

3,4-Dimethoxybenzimidamide hydrochloride (cas: 51488-33-6) belongs to ethers. The oxygen atom in ethers are more electronegative than carbon, thus the hydrogens which are alpha to the ethers are more acidic than the simple hydrocarbons. Ethers are good solvents partly because they are not very reactive. Most ethers can be cleaved, however, by hydrobromic acid (HBr) to give alkyl bromides or by hydroiodic acid (HI) to give alkyl iodides.Reference of 51488-33-6

Referemce:
Ether – Wikipedia,
Ether | (C2H5)2O – PubChem