Process for producing 1-chlorocarbonyl-4-piperidinopiperidine or hydrochloride thereof

A process for producing 1-chlorocarbonyl-4-piperidinopiperidine hydrochloride represented by the following formula (4):

• ##STR2## or 1-chlorocarbonyl-4-piperidinopiperidine represented by the following formula (5):
• ##STR3## which comprises reacting 4-piperidinopiperidine represented by the following formula (1):
• ##STR4## with a trialkylsilyl halide to obtain a 4-piperidinopiperidinyl trialkylsilyl represented by the following formula (2):
• ##STR5## wherein R.sup.1, R.sup.2 and R.sup.3 are the same or different and each independently represents a linear or branched C.sub.1-6 alkyl group;
• reacting the resulting compound with a carbon dioxide gas to obtain a 4-piperidinopiperidinyl trialkylsilyl carbamate derivative represented by the following formula (3):
• ##STR6## wherein R.sup.1, R.sup.2 and R.sup.3 have the same meanings as defined above;
• reacting the derivative with one or more substances selected from thionyl chloride, phosphorus trichloride, phosphorus pentachloride, oxalyl chloride and phosphoryl trichloride;
• and optionally reacting with a strong base.