The first series of Arrandale mobile processors, the i7's were dual cores (see also: i7-6x0m) I'll send you my paypal account for the $100
In reality, those Core i7 duals were just extra cache versions of the i5 and generally binned for higher frequencies -- and not much else.
The Core 2 Duo and the Core i3/5/7 dual cores are fundamentally different because of their architecture. Core 2 Duo series are an older architecture, each singular processor will get less work done and use more power than each singular core from an i3/i5/i7 processor. There isn't actually an "i7 core 2 quad", what you probably meant was simply "i7 quad core".
So, to answer your question: an i7 dual core only existed in mobile form (Arrandale), and an i7 quad core existed on all desktops and later laptops (Sandy Bridge.)