Aromatic Electrophilic Substitution vs. Intramolecular Wittig Reaction: Vinyltriphenylphosphonium Salt Mediated Synthesis of 4-Carboxyalkyl-8-formyl Coumarins - Majumdar, K. C.; Ansary, Inul; Samanta, Srikanta; Roy, Brindaban (Synlett, 2011)