NOVELTY - Preparation of a compound comprising at least one linear series of five fused C rings comprises: providing a compound comprising at least one quinone moiety; providing optionally substituted acyclic, cyclic or heterocyclic diene; and performing a double or stepwise cycloaddition reaction between the compound containing the quinone moiety and the diene to generate core structure of a carbonyl substituted pentacene compound (V) comprising five fused carbon rings sequentially identified as rings A, B, C, D, and E, which optionally comprises additional substituents.    USE - The process is useful in the preparation of a compound comprising at least one linear series of five fused carbon rings (claimed) which is useful in the production of electronic components (e.g. organic semiconductors of p-type and/or n-type components), devices (e.g. organic thin film transistors, organic FET, organic LED, solar energy conversion device, solar cells and inkjet fabrication device) and materials (e.g. semiconductor materials).    ADVANTAGE - The process is highly successful and flexible and provides the opportunities for the production of 2,9- or 2,10-disubstituted pentacenes comprising acetylene substituents, which are themselves very useful as intermediates for the generation of alternative substitutions or for coupling reactions. The process provides rapid synthesis of the compounds which have desirable solubility, crystal packing geometries, and electronic properties; a significant degree of flexibility with regard to the substituents located on the substrates during synthesis of the five fused carbon ring core structure; and opportunities for substituent addition or replacement.    DETAILED DESCRIPTION - Preparation of a compound comprising at least one linear series of five fused C rings comprises: providing a compound comprising at least one quinone moiety; providing optionally substituted acyclic, cyclic or heterocyclic diene; and performing a double or stepwise cycloaddition reaction between the compound containing the quinone moiety and the diene to generate core structure of a carbonyl substituted pentacene compound of formula (V) comprising five fused carbon rings sequentially identified as rings A, B, C, D, and E, which optionally comprises additional substituents.