Tetramethyl guanidine catalyst

A carbodiimide-grafted polystyrene resin was reacted with tetramethyl-guanidine to give an interesting biguanide structure (Scheme 13). This was assayed as a catalyst for a transesterification reaction.33 Incidentally, resin-bound guanidines are useful bases for processes involving resin capture.34... 

Now for the synthesis. The nitro compound 75 was made from bromopentane and a nitrite in DMSO, a good solvent for Sn2 reactions, and added to the enone 76, an acetal derived from the diketone 74 with the strong base tetramethyl guanidine 77 as catalyst to give the partly protected form 78 of 73. Now all is ready for the various reductions. 

Related catalysts. Hassner et al. have prepared a number of substituted derivatives of pyridine, pyridazine, and quinoline, but only a few are useful acylation catalysts. Of these, 4-pyrrolidinopyridine (2) and l,l,3,3-tetramethyl-4-(4-pyri-dyl)guanidine (3) are most effective. 

The same substituent effect is present with trifluoromethyl aryl ketones. N/J, AfW-Tetramethyl-N"-(f-butyl)guanidine was an effective catalyst for reaction with trifluoromethyl ketones [123]. The reaction can be done enantioselectively using 3,3 -bw-(2,4,6,-tri-j-propyl-phenyl)BlNOL [ 124],... 

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