Base‐induced isomerization of 1,4‐dialkoxy‐2‐alkynes

1,4-Dialkoxy-2-alkynes of structural types ROCH(R1)CCCH2 OR (R and R1 = alkyl) and ROC(R1)(R2)CCCH2OR (R = alkyl, R1 and R2 = alkyl or R1R2C(CH2)5) are converted into the allenic isomers under the influence of potassium tert-butoxide in dimethyl sulfoxide. 1,4-Dialkoxy-2-butynes RO-CH2CCCH2OR under these conditions yield conjugated dienes of the type ROCHCHCHCHOR; the corresponding allenes, ROCHCCHCH2OR, can be prepared by using potassium tert-butoxide in tetrahydrofuran or liquid ammonia.