Pyrans as liquid crystals

A process for preparing a tetrahydropyran compound of formula I

• in which
• R is H, or an alkyl group having 1 to 12 C atoms, which is unsubstituted or substituted by at least one halogen atom or —CN, in which one or more non adjacent CH2-groups are optionally, each independently, replaced by —O—, —S—, —CO—, —CF2—,
• CO—O—, —O—CO—, or —CH═CH—,
• A1, A2, A3 are, each independently,
• a) trans-1,4-cyclohexylene
• b) tetrahydropyran-2,5-diyl,
• c) 1,4-phenylene, in which one or more non adjacent CH-groups are optionally replaced by N,
• d) 1,4-bicyclo[2.2.2]octylene, piperidine-2,5-diyl,
• e) naphthalene-2,6-diyl,
• f) decahydronaphthalene-2,6-diyl,
• g) 1,2,3,4-tetrahydronaphthalene-2,6-diyl, or
• h) 1,4-cyclohexenylene,
• wherein the groups listed under c), e) and g) are optionally substituted with —CN, —Cl, —F or OCF3, and
• wherein at least one of the groups A1, A2, or A3 is tetrahydropyran-2,5-diyl,
• Z1 is —CO—O—, —CH2O—, —O—, —O—CH2—, —CH2CH2—, —CH═CH—, —C≡C—, or a single bond,
• m is 0, 1, or 2,
• n and p are, each independently, 0, 1 or 2,
• and m+n+p is 2, 3 or 4,
• X, Y are, each independently, —H or —F, wherein at least one of X and Y is —F, and
• Q is H, —CN, —NCS, —F, —Cl, —CF3, SF5, —OCF2CHFCF3, —OCF3, —OCHF2, —OCHFCF3, or —OCF2CF3,
• comprising a reaction that proceeds according to the following reaction scheme:
• wherein FG1 and FG2 are the following:
• -FG1
• -FG2
• ═O
• a metal containing group, which
• is Li, MgBr2, ZnBr2, ZnCl2 or Zn
• —Br
• a metal containing group, which
• is Li, MgBr2, ZnBr2, ZnCl2 or Zn
• a metal containing group,
• —Br.
• which is Li, MgBr2,
• ZnBr2, ZnCl2 or Zn