Preparation of N,N'-bridged bistetramethylpiperidinyl compounds

Details Preparation of N,N'-bridged bistetramethylpiperidinyl compounds Preparation of N,N'-bridged bistetramethylpiperidinyl compounds

1996-07-09

1998-02-03

Ivy, C. Warren

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

546 19, 546256, 546261, C07D21146

Patent

active

057146110

DESCRIPTION:

BRIEF SUMMARY
This application is a 371 of PCT/EP95/00205, Jan. 20, 1995.
The present invention relates to an improved process for the preparation of N,N'-bridged bistetramethylpiperidinyl compounds of the general formula I ##STR4## where m is 2 or 3 and the two pairs of radicals R.sup.1 /R.sup.2 are identical or different and may have the following meanings: where --CO--, --O--CO--, --O--CO--NR.sup.5 -- or O--CO--O--, up to 10 non-neighboring oxygen atoms or bridging members of the formula --NR.sup.4 -- and by up to 3 carbonyl groups, C.sub.2 -C.sub.20 -alkenyl, C.sub.3 -C.sub.12 -cycloalkyl which may be substituted by up to 3 C.sub.1 -C.sub.4 -alkyl groups, phenyl which may be substituted by up to 3 C.sub.1 -C.sub.6 -alkyl groups or hydroxyl groups, C.sub.7 -C.sub.18 -phenylalkyl which may be substituted by up to 3 C.sub.1 -C.sub.4 -alkyl groups or hydroxyl groups, C.sub.6 -C.sub.18 -cycloalkylalkyl which may be substituted by up to 3 C.sub.1 -C.sub.4 -alkyl groups, or a five-membered or six-membered unsaturated or saturated heterocyclic ring having up to 3 hetero atoms selected from the group consisting of nitrogen, oxygen and sulfur, which may additionally be benzofused and substituted by up to 3 C.sub.1 -C.sub.6 -alkyl groups or hydroxyl groups, with the proviso that R.sup.3 is not hydrogen if A is the bridging member --NR.sup.4 --, -C.sub.12 -cycloalkyl which may be substituted by up to 3 C.sub.1 -C.sub.4 -alkyl groups, C.sub.7 -C.sub.18 -phenylalkyl which may be substituted by up to 3 C.sub.1 -C.sub.4 -alkyl groups, or C.sub.6 -C.sub.18 -cycloalkylalkyl which may be substituted by up to 3 C.sub.1 -C.sub.4 -alkyl groups and -C.sub.20 -alkyloxy or C.sub.1 -C.sub.6 -alkoxycarbonyl-C.sub.2 -C.sub.20 -alkenyloxy; two radicals R.sup.6 are identical or different and are each C.sub.1 -C.sub.20 -alkyl or C.sub.2 -C.sub.20 -alkenyl, which may be substituted by up to 3 hydroxyl groups, and may be linked to form a 1,3-dioxane or a 1,3-dioxolane ring; these oxygen atoms may furthermore be etherified by groups of the structure R.sup.4 to form the corresponding enol structure on the piperidone ring; ##STR5##
Since some of the compounds I are novel substances, the present invention furthermore relates to these novel substances and to their use as light stabilizers and stabilizers for organic material. The present invention also relates to a process for the preparation of N,N'-bridged bistetramethylpiperidinyl esters.
Processes for the preparation of N-ethylene-bridged tetraalkylpiperidines are known. Thus, L.M. Kostochka, A.M. Belostotskii and A.P. Skoldinov, in Khim. Geterots. Soedinenii 1981, 1694-1695 (1) and Khim. Geterots. Soedinenii 1982, 1657-1661 (2), describe the photochemical dimerization of 1,2,2,6,6-pentamethylpiperidin-4-ol to give N,N'-ethylene-bridged bis-2,2,6,6-tetramethylpiperdin-4-ol (compound I in which m is 2, R.sup.1 is H and R.sup.2 is OH). In addition to an unsatisfactory yield, however, this method has further disadvantages. Thus, many byproducts are formed and necessitate expensive purification. The exposure to light is technically complicated and hence uneconomical. For the preparation of the bridged product, the N-methylated derivative must first be prepared in an additional stage from the industrially readily available 2,2,6,6-tetramethylpiperidin-4-ol.
Example 1 of German Laid-Open Application DOS 2,338,076 (3) describes the preparation of 1,2-bis(4-benzoyloxy-2,2,6,6-tetramethylpiperidino)ethane by reacting N-unsubstituted 4-benzoyloxy-2,2,6,6-tetramethylpiperidine with 1,2-dibromoethane. This procedure has the serious disadvantage that the highly toxic 1,2-dibromoethane is used as a reagent. Furthermore, the subsequent expensive working up of the reaction mixture by extraction with benzene (which is likewise toxic), washing, evaporating down, washing again and recrystallizing suggests that this reaction too is nonselective with respect to the desired product. The bridged piperidine derivatives stated in (3) are recommended as light and heat stabilizers for synthetic polymers.
It is an object of th

REFERENCES:
patent: 3940363 (1976-02-01), Murayama et al.

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