Synthesis of dihydrofurans substituted in the 2-position

Many natural products and biologically active compounds contain the dihydrofuran subunit. Molecules incorporating either 2-substituted, 2,2-disubstituted 2,3- or 2,5-dihydrofurans are widespread in the literature and represent key "molecular building blocks". The preparation of substituted dihydrofurans remains a current challenge in organic synthesis and this microreview details the various routes employed for their synthesis in the literature to the end of 2004.