2‐Cyanoacrylates as reagents in heteroatomic synthesis (a review)

Abstract

AbstractSeveral types of addition reactions to the CC bond of alkyl 2‐cyanoacrylates, CH2C(CN)COOR (1), are considered. The first examples deal with addition of CH‐Acids (pKa less than 13) and of H2S in the presence of catalytic amounts of strong amines, also of mercaptans, thiocarboxylic, and thiophosphoric acids. P‐Sulfenylchlorides and acidic phosphites add irreversibly at 20°C to form addition products in accordance with the distribution of charges in 1. HCl reversibly adds to 1 and to the acid chloride CH2C(CN)COCl (2). Alcohols and H2O also add reversibly to the acid CH2C(CN)COOH (3) and to esters of 1 to transform 1 and 3 into polymers. Triethylsilane in the presence of CF3COOH (4) reduces the CC bond of 1 and 3 to the corresponding saturated derivatives.The second set of examples involves reactions of 1 with P‐III compounds in the presence or absence of 4. Ph3P as well as other weak nucleophiles reversibly add to 1 in the absence of 4 to cause instant polymerization. However, 4 protonates an initially formed zwitter‐ion in the reaction of 1 with Ph3P,(EtO)2PCl,Ph2PCl and thiourea to afford stable addition products. IR spectroscopy reveals the formation of H‐complexes of 4 with the CN and COOR groups of 1, which stimulates the addition of the weak nucleophile (o‐C6H4O2)PCl to the CC bond of 1. This reagent does not react with 1 in the absence of 4. Strong nucleophiles, Alk3P, and (Et2N)3P in excess irreversibly add at 20°C to 1 to form zwitterions, which specifically react with PhNCO to give stable products. 1,3,2‐Dioxaphospholes react with 1 either to form spirophosphoranes or 2‐cyano‐3‐phosphoranylpropionates.