Acrylamide photoinitiators

A method for synthesising the photoinitiators of the general formula (I),

• wherein R1 is H or an optionally substituted C1-C6 alkyl;
• PI is a photoinitiator selected from the group consisting of benzoin ethers, 1-phenyl-2-hydroxy-2-alkyl ketones, 1-phenyl-2-amino-2-alkyl ketones, dibenzosuberones, benzils, benzil ketals, acetophenones, α-alkoxy-acetophenones, α,α-dialkoxy-acetophenones, α-hydroxy-α-alkyl-phenones, α-hydroxy-α, α-dialkyl-phenones, alkyl phenylglyoxylates, camphorquinones, acyl-phosphine oxides and phenyl ketocoumarins;
• and
• R2 is H or an optionally substituted C1-C6 alkyl, said method comprising steps a) and b):
• wherein step a) comprises reacting an alcohol of the general formula IIa
• wherein Za is a linker moiety comprising a single bond, C1-C12 alkylene, C1-C12 alkenylene, —O—, —S—, —NRa—, or —[O—(C1-C12 alkylene)]n—, wherein Ra is H or optionally a substituted C1-C12 alkyl and n is an integer from 1-20;
• and
• R3 and R4 are each independently a H or an optionally substituted C1-C6 alkyl;
• wherein R3 or R4, or a portion of R3 or R4, can be linked to Za to form one or more ring structures;
• with an acrylonitrile of the general formula IIb
• wherein R1 is H or an optionally substituted C1-C6 alkyl;
• in a Ritter reaction to form an acrylamide of the general formula IIc:
• wherein step b) comprises reacting the acrylamide of the general formula IIc in a Friedel-Crafts acylation reaction to provide the photoinitiator of formula (I).