Phosphorylated 5-tert-Butyl-2 and 3-Furylalkenes: Synthesis and Heterocyclization

By the reaction of 5-tert-butyl-2- and -3-furoyl phosphonates with acylmethylenetriphenylphosphoranes a series of 1-R-1-oxo-3-(3-methyl-5-tert-butylfuran-2-yl)- and -R-1-oxo-3-(3-methyl-5-tert-butylfuran-3-yl)-3-(diethoxyphosphoryl)-2-propenes was synthesized. It was shown that depending on R nature and location of alkene fragment in the furan ring in the reactions with hydrazine and its derivatives hydrazones or pyrazolines, the products of consequent addition at the double bond, are formed. Diethyl (Е)-{1-[5-(tert-butyl)-3-(methyl)furan-2-yl]-3-oxobut-1-en-1-yl}phosphonate semicarbazone is oxidized with selenium dioxide to corresponding 1,2,3-selenodiazole. 3-(3-Formyl-5-tert-butylfuran-2-yl)-3- and 3-(2-formyl-5-tert-butylfuran-3-yl)-3-(diethoxyphosphoryl)acrylates are synthesized. When treated with hydrazine hydrate they undergo cyclization to the derivatives of 5,6-dihydro-4Н-furo[2,3-d][1,2]diazepine and 7,8-dihydro-6Н-furo[3,2-d][1,2]diazepine respectively. Diethyl (Е)-{1-[5-(tert-butyl)-2-(sulfanylmethyl)furan-3-yl]-3-oxo-3-phenylprop-1-en-1-yl} phosphonate undergo spontaneous cyclization to the derivative of 5-benzoyl-4,7-dihydro-5Н-thiopyrano[3,4-b]furan, while at the reversed location of substituents nuclephylic addition to the double bond does not proceed.