Alkylation method

A method to obtain a compound of Formula I:

• wherein:
• (i) X1 is an X group selected from C1-4 alkyl or halo;
• Y1 is a Y group selected from hydrogen or C1-4 alkyl;
• Z1 is a Z group which is C1-4 alkyl;
• and,
• Q is [11C]C1-4 alkyl- or [18F]-C1-4fluoroalkyl-;
• wherein said method comprises:
• (ii) reducing a compound of Formula II:
• wherein:
• (ii) X11 and X12 are the same and are both an X group as defined for X1;
• Y11 and Y12 are the same and are both a Y group as defined for Y1;
• and,
• Z11 and Z12 are the same and are both a Z group as defined for Z1;
• and,
• (ii) adding a base to the product of step (i) and reacting with either [11C]C1-4 alkyl-LG1 or [18F]-C1-4 fluoroalkyl-LG2, wherein LG1 and LG2 are independently halo, or the group —O—SO2—R1 wherein R1 represents an optionally-substituted C6-10 aryl, an optionally-substituted C1-4 alkyl, or C1-4 fluoroalkyl;
• wherein the molar ratio of added base:thiol in step (ii) is in the range of about 0.2-1.0.