The Synthetic Routes of THIENO[3,2-D]PYRIMIDIN-4(3H)-ONE

Introduction:

The synthesis of thieno[3,2-d]pyrimidin-4(3H)-one, also known as 2,3-dihydro-2,3-benzoxazepine-1,4-dione, is an important synthetic goal in the chemical industry due to its wide range of applications in pharmaceuticals, agrochemicals, and other industries.
In this article, we will discuss the various synthetic routes to thieno[3,2-d]pyrimidin-4(3H)-one, which have been developed over the last few decades.

Synthetic Routes to Thieno[3,2-d]pyrimidin-4(3H)-one:

1. Hydrolysis of N-benzyloxycarbonyl-L-histidine: One of the most common methods of synthesizing thieno[3,2-d]pyrimidin-4(3H)-one involves the hydrolysis of N-benzyloxycarbonyl-L-histidine, which is an intermediate in the synthesis of histamine.
   This reaction involves the reaction of 2,4-dichloro-3-nitroaniline with L-histidine in the presence of a base, followed by benzylation of the intermediate using benzyl bromide.
   The resulting N-benzyloxycarbonyl-L-histidine is then hydrolyzed using a strong acid to yield thieno[3,2-d]pyrimidin-4(3H)-one.
   
2. Reduction of N-benzyloxycarbonyl-5-methyl-2,4-dihydroxypyrimidine: Another synthetic route to thieno[3,2-d]pyrimidin-4(3H)-one involves the reduction of N-benzyloxycarbonyl-5-methyl-2,4-dihydroxypyrimidine, which is an intermediate in the synthesis of various herbicides.
   This reaction involves the reduction of N-benzyloxycarbonyl-5-methyl-2,4-dihydroxypyrimidine using a reducing agent such as lithium aluminum hydride, which leads to the formation of thieno[3,2-d]pyrimidin-4(3H)-one.
   
3. Cyclization of 5,6-dihydro-5,6-dihydroxy-2H-pyrimidin-2-one: Thieno[3,2-d]pyrimidin-4(3H)-one can also be synthesized by the cyclization of 5,6-dihydro-5,6-dihydroxy-2H-pyrimidin-2-one, which is an intermediate in the synthesis of various nitrogen-containing compounds.
   This reaction involves the reaction of 5,6-dihydro-5,6-dihydroxy-2H-pyrimidin-2-one with an aromatic aldehyde in the presence of a strong acid, followed by cyclization to yield thieno[3,2-d]pyrimidin-4(3H)-one.
   
4. Decarboxylation of N-(thiocyanomethylene)histamine: Another synthetic route to thieno[3,2-d]pyrimidin-4(3H)-one involves the decarboxylation of N-(thiocyanomethylene)histamine, which is an intermediate in the synthesis of histamine.
   This reaction involves the treatment of N-(thiocyanomethylene)histamine with a strong acid, followed by decarboxylation to yield thieno[3,2-