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A series of methylidene substituted 2,5-dihydrofurans is prepared via the reaction of ethyl 5,5-diphenylpenta-2,3,4-trienoate (I) with aryl or hetaryl aldehydes.

A Lewis acid promoted tandem reaction of epoxide rearrangement and intramolecular [3+2] cycloaddition reaction of cyclopropanes with carbonyls formed by epoxide rearrangement in situ, which were obtained with difficulty by a general method, is reported. A wide variety of fused- and spiro-oxa-[n.2.1] skeletons could be efficiently constructed.

Photovoltaic cells are considered to be one of the most promising renewable energy sources of the 21st century. In particular, dye-sensitized solar cells (DSSCs) and organic photovoltaic devices (OPVs) are potentially the most economical and environmentally friendly ones. Squaraine (SQ) has intense absorption at 600–850 nm, exactly where sun flux is the most abundant. Furthermore, various substituents on SQ cores provide great possibilities for different molecular-design strategies. These characters make SQs ideal candidates for new DSSCs and OPVs. In response to the rapid development of SQ-based solar cells, a panorama of these ongoing studies is presented here, including the general synthetic routes of SQs and the various SQs used in DSSCs and OPVs. Our discussions are focused on the diverse molecular designs of SQs used in DSSCs and OPVs. The design strategies to acquire better light-harvesting abilities are also provided here, as well as the principles behind these strategies.

The reactions can be performed without microwave irradiation providing the corresponding products after significantly longer reaction times in lower yields.