Processes for the preparation of 3,4-substituted-1,2,5-thiadiazoles and intermediates thereof

A compound of formula I

• wherein
• L is a leaving group;
• R1 and R2 are independently selected from the group consisting of hydrogen, C1-C4 alkyl, benzyl optionally substituted with one or more substituents independently selected from the group consisting of halo, C1-C4 alkyl, C1-C4 alkoxy and —CF3;
• and —SiRRR wherein each R is independently selected from the group consisting of C1-C4 alkyl, and phenyl optionally substituted with one or more substituents independently selected from the group consisting of C1-C4 alkyl, and C1-C4 alkoxy;
• provided when R1 is hydrogen then R2 is not hydrogen;
• or
• R1 and R2 are taken together with the nitrogen in which they are attached to form a ring of formula II
• wherein
• X is selected from the group consisting of bond, —CH2—, —S(O)—n, —O— and —NR21— wherein R21 is selected from the group consisting of C1-C4 alkyl, benzyl and phenyl optionally substituted with one or more substituents independently selected from the group consisting of halo, C1-C4 alkyl, and —CF3;
• n is 0, 1 or 2;
• and
• Q is selected from the group consisting of a bond, a carbon atom wherein each R4 is independently selected from the group consisting of hydrogen and C1-C4 alkyl;
• and a silicon atom wherein each R4 is independently selected from the group consisting of C1-C4 alkyl and phenyl.