Intramolecular Prins reaction and catalysts suitable therefor

1. A process for the preparation of a compound of the formula B

comprising:

providing a compound of the formula A

reacting the compound of the formula A in an intramolecular reaction in the presence of an aluminium siloxide of the formula (Ia) or (Ib)

wherein R 1 , R 2 , R 3 in each case independently of one another are hydrogen or methyl,

R 4 is hydrogen or an alkyl radical having 1 to 6 C atoms,

n is 0, 1 or 2; and

R a′ , R a″ , R a′″ in each case independently of one another and, for formula (Ib), independently of the meaning in a second substituent —SiR a′ R a″ R a′″ are hydrogen or an organic radical, with the proviso that at least one of the radicals R a′ , R a″ , R a′″ of each substituent —SiR a′ R a″ R a′″ is not hydrogen; and

independently of one another two or three of the radicals R a′ , R a″ , R a′″ of each substituent —SiR a′ R a″ R a′″ may be covalently bonded to one another; and

X in each case independently is an organic or inorganic substituent, but not hydrogen or a siloxy group having a substituent —SiR a′ R a″ R a′″ as defined above.

2. The process of claim 1 , wherein in each case X independently is an organic or inorganic substituent which is chosen from the group consisting of branched or unbranched or cyclic alkyl, alkenyl or alkynyl having 1 to 30 C atoms; alkoxy having 1 to 30 C atoms; cycloalkoxy having a ring size of C 3 -C 16 ; aryloxy; bisaryloxy; boric acid substituted by one or two organic radicals; and chloride.

3. The process of claim 1 , wherein each X independently is methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, alkoxy having 1 to 10 C atoms, cycloalkoxy having a ring size of C 3 -C 8 or chloride.

4. The process of claim 1 , wherein

R 1 and R 2 in each case independently of one another are hydrogen or methyl,

R 3 is hydrogen,

R 4 is methyl, and

n is 0 or 1.

5. The process of claim 1 , wherein the compound of the formula A is selected from the group consisting of 2,6-dimethyl-5-heptenal and citronellal (3,7-dimethyl-6-octenal).

6. The process of claim 1 , wherein the intramolecular reaction of the compound of the formula A is carried out in a diluent, the boiling point of which is higher than that of the compounds of the formulae A and B; or

after the intramolecular reaction of the compound of the formula A has taken place, a diluent, the boiling point of which is higher than that of the compounds of the formulae A and B, is added,

said process further comprising:

separating off, by distillation, the compound of the formula B from the diluent and the aluminium siloxide of the formula (Ia) or (Ib).

7. The process according to claim 1 , further comprising:

recycling the aluminium siloxide of the formula (Ia) or (Ib) in the intramolecular reaction of the compound of the formula A.

8. The process of claim 1 , wherein R a′ , R a″ , R a′″ in each case independently are a substituted or unsubstituted radical which is chosen from the group consisting of C 1 -C 20 -alkyl, C 1 -C 20 -heteroalkyl, C 3 -C 20 -cycloalkyl, C 4 -C 20 -cycloalkylalkyl, C 2 -C 20 -alkenyl, C 3 -C 20 -cycloalkenyl, C 4 -C 20 -cycloalkenylalkyl, C 2 -C 20 -alkynyl, C 5 -C 20 -cycloalkylalkynyl, C 1 -C 20 -alkoxy, C 3 -C 20 -cycloalkoxy, C 5 -C 20 -cycloalkylalkoxy, C 3 -C 25 -aryl, C 2 -C 25 -heteroaryl, C 4 -C 25 -arylalkyl, C 8 -C 25 -cycloalkylaryl, C 8 -C 25 -cycloalkenylaryl, C 5 -C 25 -cycloalkylheteroaryl, C 8 -C 25 -heterocycloalkylaryl, C 8 -C 25 -heterocycloalkenylaryl, and C 8 -C 25 -heterocycloalkenylheteroaryl and C 3 -C 25 -heteroarylalkyl,

wherein independently of one another also two or three of the radicals R a′ , R a″ , R a′″ can be covalently bonded to one another.

9. The process of claim 1 , wherein R a′ , R a″ , R a′″ in each case independently are an optionally substituted radical chosen from the group consisting of C 3 -C 25 -aryl, C 2 -C 25 -heteroaryl, C 4 -C 25 -arylalkyl, C 8 -C 25 -cycloalkylaryl, C 8 -C 25 -cycloalkenylaryl, C 5 -C 25 -cycloalkylheteroaryl, C 8 -C 25 -heterocycloalkylaryl, C 8 -C 25 -heterocycloalkenylaryl, C 8 -C 25 -heterocycloalkenylheteroaryl and C 3 -C 25 -heteroarylalkyl.

10. The process of claim 1 , wherein

R a′ , R a″ , R a′″ in each case independently are a substituted or unsubstituted radical chosen from the group consisting of C 6 -C 20 -aryl, C 3 -C 20 -heteroaryl, C 8 -C 20 -cycloalkylaryl, C 8 -C 20 -cycloalkenylaryl, C 7 -C 20 -cycloalkylheteroaryl, C 8 -C 20 -heterocycloalkylaryl, C 8 -C 20 -heterocycloalkenylaryl and C 8 -C 20 -heterocycloalkenylheteroaryl.

11. The process of claim 1 , wherein all the radicals R a′ , R a″ , R a′″ are identical.

12. A process for the preparation of a compound of the formula B

comprising:

(a) providing a compound of the formula A

(b) reacting an aluminium compound of the formula (IIIa) or (IIIb)

wherein

each R 5 is the same or different and is an alkyl radical having 1 to 4 C atoms or an aryl radical or hydrogen; and

X is an alkyl radical having 1 to 4 C atoms or chloride,

with the proviso that X is bonded to Al more firmly than or as firmly as R 5 ;

with one or more different silanols of the formula (II),

wherein:

R a′ , R a″ , R a′″ in each case independently are hydrogen or an organic radical, with the proviso that at least one of the radicals R a′ , R a″ , R a′″ in each silanol employed is not hydrogen;

independently of one another also two or three of the radicals R a′ , R a″ , R a′″ in each of the silanols employed can be covalently bonded to one another; and

the molar ratio of aluminium compound of the formula (IIIa) or (IIIb) to the total amount of the one or more different silanols of the formula (II) is greater than 1:3; and

(c) in situ and/or within 1 hour after the start of the reaction according to step (b), contacting of the compound of the formula A with the reaction product obtained in step (b) under conditions such that an intramolecular reaction of the compound of the formula A occurs to produce a compound of the formula B;

wherein R 1 , R 2 , R 3 in each case independently of one another are hydrogen or methyl,

R 4 is hydrogen or an alkyl radical having 1 to 6 C atoms, and

n is 0, 1 or 2.

13. The process of claim 12 , wherein

R 1 and R 2 in each case independently of one another are hydrogen or methyl,

R 3 is hydrogen,

R 4 is methyl, and

n is 0 or 1.

14. A process comprising undergoing a chemical reaction in the presence of a catalyst selected from the group consisting of:

an aluminium siloxide of the formula (Ia) or (Ib)

wherein X in each case independently is an organic or inorganic substituent;

a reaction product of a reaction of an aluminium compound of the formula (IIIa) or (IIIb)

wherein

R 5 is an alkyl radical having 1 to 4 C atoms, an aryl radical or hydrogen, and

X is an alkyl radical having 1 to 4 C atoms or chloride,

with the proviso that X is bonded to Al more firmly than or as firmly as R 5 ;

with one or more different silanols of the formula (II),

wherein the molar ratio of aluminium compound of the formula (IIIa) or (IIIb) to the total amount of the one or the various silanols of the formula (II) is greater than 1:3, and further wherein in formula Ia, Ib, and II

R a′ , R a″ , R a′″ in each case independently are hydrogen or an organic radical, with the proviso that at least one of the radicals R a′ , R a″ , R a′″ in each silanol or siloxide employed is not hydrogen, and

independently of one another also two or three of the radicals R a′ , R a″ , R a′″ in each of the substituents —SiR a′ R a″ R a′″ or each of the silanols employed may be covalently bonded to one another.

15. The process of claim 14 , wherein the chemical reaction is an intramolecular Prins reaction.

16. The process of claim 14 , wherein the chemical reaction produces a compound of the formula B

from a compound of the formula A

wherein in the formulae A and B, R 1 , R 2 , R 3 , R 4 and n in each case have the same meaning and

R 1 , R 2 , R 3 in each case independently of one another are hydrogen or methyl,

R 4 is hydrogen or an alkyl radical having 1 to 6 C atoms, and

n is 0, 1 or 2.