Patent ID: 8466318

Claim:
A method of preparing a compound of formula (1a), wherein R 1 and R 2 each independently denote hydrogen or a group selected from among C 1-8 alkyl, C 3-8 cycloalkyl, C 4-12 cycloalkylalkyl, 5-6 membered heteroaryl and 3-8 membered heterocycloalkyl, optionally substituted by one or more identical or different R a and/or R b , or R 1 and R 2 together with the nitrogen atom to which they are bound form a 3-14 membered heterocycloalkyl or 5-12 membered heteroaryl, this ring system optionally being substituted by one or more identical or different R a and/or R b , and each R a is independently selected from among C 1-6 alkyl, 2-6 membered heteroalkyl, C 1-6 haloalkyl, C 3-10 cycloalkyl, C 4-16 cycloalkylalkyl, C 6-10 aryl, C 7-16 arylalkyl, 5-12 membered heteroaryl, 6-18 membered heteroarylalkyl, 3-8 membered heterocycloalkyl and 4-14 membered heterocycloalkylalkyl, and each R b is independently selected from among —OR c , C 1-3 haloalkyloxy, —OCF 3 , —SR c , —NR c R c , —ONR c R c , —N(OR c )R c , —N(R c )NR c R c , halogen, —CF 3 , —CN, —NC, —OCN, —SCN, —NO, —NO 2 , —N 3 , —S(O)R c , —S(O)OR c , —S(O) 2 R c , —S(O) 2 OR c , —S(O)NR c R c , —S(O) 2 NR c R c , —OS(O)R c , —OS(O) 2 R c , —OS(O) 2 OR c , —OS(O)NR c R c , —OS(O) 2 NR c R c , —C(O)R c , —C(O)OR c , —C(O)SR c , —C(O)NR c R c , —C(O)N(R c )NR c R c , —C(O)N(R c )OR c , —C(NR c )NR c R c , —C(NOH)R c , —C(NOH)NR c R c , —OC(O)R c , —OC(O)OR c , —OC(O)SR c , —OC(O)NR c R c , —OC(NR c )NR c R c , —SC(O)R c , —SC(O)OR c , —SC(O)NR c R c , —SC(NR c )NR c R c , —N(R c )C(O)R c , —N[C(O)R c ] 2 , —N(OR c )C(O)R c , —N(R c )C(NR c )R c , —N(R c )N(R c )C(O)R c , —N[C(O)R c ]NR c R c , —N(R c )C(S)R c , —N(R c )S(O)R c , —N(R c )S(O)OR c , —N(R c )S(O) 2 R c , —N[S(O) 2 R c ] 2 , —N(R c )S(O) 2 OR c , —N(R c )S(O) 2 NR c R c , —N(R c )[S(O) 2 ] 2 R c , —N(R c )C(O)OR c , —N(R c )C(O)SR c , —N(R c )C(O)NR c R c , —N(R c )C(O)NR c NR c R c , —N(R c )N(R c )C(O)NR c R c , —N(R c )C(S)NR c R c , —[N(R c )C(O)] 2 R c , —N(R c ) [C(O)] 2 R c , —N{[C(O)] 2 R c } 2 , —N(R c )[C(O)] 2 OR c , —N(R c )[C(O)] 2 NR c R c , —N{[C(O)] 2 OR c } 2 , —N{[C(O)] 2 NR c R c } 2 , —[N(R c )C(O)] 2 OR c , —N(R c )C(NR c )OR c , —N(R c )C(NOH)R c , —N(R c )C(NR c )SR c and —N(R c )C(NR c )NR c R c , and each R c independently denotes hydrogen or C 1-6 alkyl, comprising hydrogenating a compound of formula (2a) wherein R 1 and R 2 are as defined above in the presence of platinum(IV)-dioxide as catalyst and a solvent under hydrogen pressure, wherein the hydrogenation is carried out without any addition of acids.