2 together with the carbons they are attached to form a 5 membered or 6 membered fused ring the compound has the structure of formula 2 or formula 3 wherein x 1 x 2 and x 3 are independently u2014 o u2014 u2014 s u2014 u2014 n r 4 u2014 or u2014 c h r 4 u2014 z 1 z 2 z 3 and z 4 are independently u2014 o u2014 u2014 s u2014 u2014 n r 4 u2014 or u2014 c h r 4 u2014 r 3 is hydrogen alkyl aryl or heterocyclo and r 4 is independently hydrogen alkyl aryl or heterocyclo for the compounds of formula 2 x 1 x 2 and x 3 can independently be u2014 o u2014 or u2014 c h r 4 u2014 wherein at least one of x 1 x 2 and x 3 is u2014 c h r 4 u2014 further for compounds of formula 3 z 1 z 2 z 3 and z 4 can independently be u2014 o u2014 or u2014 c h r 4 u2014 and wherein at least two of z 1 z 2 z 3 and z 4 is u2014 c h r 4 u2014 for the compounds of formula 2 preferably x 1 x 2 and x 3 can independently be u2014 c h r 4 u2014 wherein r 4 is hydrogen further for compound of formula 3 z 1 z 2 z 3 and z 4 can independently be u2014 c h r 4 u2014 wherein r 4 is hydrogen for the methods using compounds of formula 1 r 1 r 2 and r 3 can be independently alkyl preferably for the compounds of formula 1 r 1 r 2 and r.