Disclosed is a process for preparing 2,2,6,6-tetramethyl-3,5-heptanedione, comprising reacting a pivalic acid alkyl ester with pinacolone in the presence of an alkali metal alkoxide catalyst using a pivalic acid alkyl ester as a solvent but using no other solvent or reacting them in an amide type or urea type solvent in the presence of an alkali metal alkoxide catalyst. The system gives a user of the interface the full capability to relocate, re-orient, scale and layout images in the circular interface. A decoder uses ZigZag deconvolution to generate constraint node messages as part of an iterative belief propagation to decode the source bit sequence from the received multi-level symbols. Thus, this conventional method has problems that it requires a lot of time in processing the mail item.