Reactions of Epoxides - Nucleophilic Ring Opening

 Epoxides experience a great deal of ring strain and as such are rather reactive.  They undergo ring-opening reactions under acidic or basic/nucleophilic conditions.

Nucleophilic Ring Opening

In nucleophilic ring-opening the epoxide is initially attacked by the nucleophile.  Epoxides are unstable because of ring strain and are rather good electrophiles.  A variety of nucleophiles including -OH, amines, Grignard reagents, NaCN, and alkoxides (NaOR).

For example, treating ethylene oxide with NaOH followed by an acidic water quench results in ethylene glycol.

The nucleophile always attacks the least substituted carbon (S_N2 like).  Typically a quench is required to protonate the alkoxide as shown in the second step above.

Nitriles are prepared by treating epoxides with NaCN.

Ethers are prepared if alkoxides are utilized.

Application to Cardura Synthesis

In the synthesis of Cardura, intermediate 2 is synthesized by way of an epoxide ring opening followed by an intramolecular S_N2 reaction.  Can you draw the mechanism for this step?