Process for production of carebastine

1. A process for preparing piperidine derivative compound of the formula II:

wherein

R 4 is H, alkyl or aryl;

A, B, and D are the substituents of their rings, each of which may be different or the same, and are selected from the group consisting of hydrogen, fluorine, chlorine, alkyl, aryl, hydroxyl, alkoxy, and aryloxy;

said process comprising:

(a) reducing with a borohydride a compound of formula VIa

wherein

X is a group chosen from chlorine, bromine, iodine, —OSO 2 R 5 , and diazonium salt displaceable via oxidative metallic addition; and

LG is a leaving group displaceable by a secondary amine, said leaving group chosen from chlorine, bromine, iodine, and —OSO 2 R 5 , wherein R 5 is chosen from alkyl, fluoro, fluoroalkyl, aryl, and substituted aryl, or LG is a group able to be converted to said leaving group displaceable by a secondary amine, said leaving group chosen from chlorine, bromine, iodine, and —OSO 2 R 5 , under conditions to provide a compound of XXIII

(b) reacting a compound of formula XXIII with an isobutyrate equivalent compound of formula IV

wherein R 8 is a trialkylsilyl,

in the presence of a transition metal catalyst having a metal selected from the group comprising of Ni and Pd, and ZnF 2 to provide an α,α-dimethyl-4-(hydroxybutyl)-phenylacetate of the formula XIII:

(c) reacting said α,α-dimethyl-4-(hydroxybutyl)-phenylacetate of formula XIII with a protected 4-hydroxypiperidine to provide a protected α,α-dimethyl-4-([4-(hydroxy)piperidino]hydroxybutyl)-phenylacetate;

(d) deprotecting said protected α,α-dimethyl-4-([4-(hydroxy)piperidino]hydroxybutyl)-phenylacetate to provide a α,α-dimethyl-([4-(hydroxy)piperidino]hydroxybutyl)-phenylacetate of formula XIIA

(e) converting the compound of formula XIIa to II by reacting with a benzhydryl component of formula XIV;

wherein LG′ is a leaving group displaceable by OH or O Θ resulting from the deprotonation of the piperidinyl hydroxyl group of compound XV.

2. A process according to claim 1 for preparing carebastine wherein a compound of formula XIIab

is reacted, in the presence of a base, with a benzhydryl component of formula XIVa;

wherein LG′ is a leaving group, said leaving group chosen from chlorine, bromine, iodine, and —OSO 2 R 5 , wherein R 5 is chosen from alkyl, fluoroalkyl, aryl, and substituted aryl, displaceable by OH or O Θ resulting from the deprotonation of the piperidinyl hydroxyl group of compound XVa, and carrying out further process steps of oxidation and saponification to provide carebastine.

3. A process according to claim 1 wherein X is displaced by the isobutyrate equivalent compound of formula IV by reaction in the presence of a phosphorus compound chosen from trialkyl phosphine, triaryl phosphine, and mixed alkyl/aryl phosphine, and the transition metal catalyst.

4. A process according to claim 1 wherein R 8 is α-trimethylsilyl group.

5. A process according to claim 1 or 2 wherein LG′ is chosen from iodine, bromine, chlorine, methanesulfonate, toluenesulfonate, and triflate.