Synthesis of para-alkylated syringyl (meth)acrylate derivatives and photopolymerizable compositions for additive manufacturing in dental applications

An orthodontic appliance comprising a polymeric material obtainable by curing a composition comprising:

• a compound having the structure of Formula (I), or a salt or solvate thereof:
• wherein:
• R1 is H, halogen, C1-C6 alkyl, C1-C6 alkenyl, C1-C6 alkynyl, C1-C6 cycloalkyl, C1-C6 heterocycloalkyl, —OR9, or —N(R9)2;
• each instance of R2, R3, and R4 is independently selected from the group consisting of C1-C6 alkyl, C1-C6 alkenyl, C1-C6 alkynyl, C1-C6 cycloalkyl, C1-C6 heterocycloalkyl, —OR9, and —N(R9)2;
• or optionally any two of R2, R3, and R4 are taken together along with the carbon to which they are commonly attached to form C1-C8 cycloalkyl or C1-C8 heterocycloalkyl;
• or optionally R2, R3, and R4 are taken together along with the carbon to which they are commonly attached to form a caged ring;
• R5, R6, R7, and R8 are each independently selected from the group consisting of H, halogen, C1-C6 alkyl, C1-C6 alkenyl, C1-C6 alkynyl, —OR9, —N(R9)2, —(C═O)—R9, —O—(C═O)—R9, and —(NR9)—(C═O)—R9;
• each instance of R9 is independently selected from the group consisting of H, C1-C6 alkyl, C1-C6 alkenyl, and C1-C6 alkynyl;
• each instance of R1, R2, R3, R4, R5, R6, R7, and R8 is independently optionally substituted with one or more instances of R10;
• and
• each instance of R10 is independently selected from the group consisting of ═O, halogen, C1-C4 alkyl, C1-C4 alkenyl, C1-C4 alkynyl, —OR9, —N(R9)2, —(C═O)—R9, —O—(C═O)—R9, and —(NR9)—(C═O)—R9;
• and
• X1 is C(R9)2, NR9, O or S;
• and
• an oligomer comprising a glass transition temperature (Tg) of at most −10° C.