The coupling of a variety of aromatic ring-substituted alkynylbenzaldehydes with 3-butenylcarbene complexes has been examined.  The reaction course is highly dependent on the electron density at the benzene ring.  Electron rich systems afford the dihydrophenanthrenes, while electron poor systems afford enone-alcohols.  Formation of the dihydrophenanthrene was attributed to formation of a benzylic carbocation para to the X group in an oxanorbornene intermediate, followed by alkene formation and dehydration.  This process can be prevented if X is electron withdrawing.