211  US 9,256,127 B2  212  -continued  wherein R $^{1 }$is hydrogen, methyl or trifluoromethyl, R $^{2 }$and R 3  are each independently hydrogen or a straight, branched or  cyclic, monovalent hydrocarbon group of  1  to  10  carbon  atoms, R 2  and R 3  may bond together to form an alicyclic  group of 5 to  10  carbon atoms, which may be separated by an  35  oxygen atom or have a carbon chain, with the carbon atom to  which they are attached, X$^{1 }$is a straight, branched or cyclic,  divalent hydrocarbon group of  1  to 20 carbon atoms in which  a constituent ----CH$_{2}$ - may be replaced by ---0- or  -C(=O)-, k$^{1 }$is 0or  1,  Zforms a5 or6-memberedalicyclic 40  group, which may contain a heteroatom, with the two carbon  atoms to which it is attached, X $^{4 }$is hydrogen or halogen, and  R $^{4 }$is a straight, branched or cyclic, monovalent hydrocarbon  group of  1  to  10  carbon atoms.  13.  The method of claim  12  wherein the acyloxyketone  having the general formula (5) is obtained by reacting a  cycloalkanone compound having the general formula (3)  with an esterifying agent having the general formula (  4):  wherein R  1 , X  1 , Z and k $^{1 }$are as defined above, X$^{2 }$is halogen  or hydroxyl, X$^{3 }$is---OM 6 , halogen, hydroxyl or-OR 1 4 , M 6  is Li, Na, K, Mg$_{112}$, Ca 112  or substituted or unsubstituted  ammonium, and R $^{14 }$is methyl, ethyl or a group of the formula  (9):  wherein R1, X$^{1 }$and k$^{1 }$are as defined above, and the broken  line denotes a valence bond.  14.  A method for preparing a monomer having the general  formula  (1),  comprising the steps of reacting a compound  having the general formula ( 6) with a base or metal to form a  metal enolate reagent, reacting it with an acyloxyketone hav› ing the general formula (5), isolating a hydroxy ester com› pound having the general formula (7b ), and treating it with an  acid:  wherein R $^{1 }$is hydrogen, methyl or trifluoromethyl, R $^{2 }$and R 3  are each independently hydrogen or a straight, branched or  cyclic, monovalent hydrocarbon group of  1  to  10  carbon  atoms, R 2  and R 3  may bond together to form an alicyclic  group of 5 to  10  carbon atoms, which may be separated by an  (5)  (1) (3) (4)  (6)  (5)  (7b)  (1)  (9) 