Organocatalytic carbonyl-olefin metathesis.

The development of a catalytic carbonyl-olefin metathesis strategy is reported, in the context of the ring-opening metathesis of cyclopropenes with aldehydes using a simple hydrazine catalyst. The key to this reaction is a conceptual blueprint for metathesis chemistry that forgoes the traditional reliance on [2 + 2] cycloaddition modes in favor of a [3 + 2] paradigm.

Photoinduced C-N bond cleavage in 2-azido-1,3-diphenyl-propan-1-one derivatives: photorelease of hydrazoic acid.

Photolysis of 3-azido-1,3-diphenyl-propan-1-one (1a) in toluene yields 1,3-diphenyl-propen-1-one (2), whereas irradiation of 3-azido-2,2-dimethyl-1,3-diphenyl-propan-1-one (1b) results in the formation of mainly 2,2-dimethyl-1,3-diphenyl-propan-1-one. Laser flash photolysis (308 nm) of 1a,b in acetonitrile reveals a transient absorption (lambda max = approximately 310 nm) due to the formation of radicals 4a and 4b, respectively, which have lifetimes of approximately 14 micros at ambient temperature. TD-DFT calculations (B3LYP/6-31+G(d)) reveal that the first and second excited states of the triplet ketone (T1K (n,pi*) and T2K (pi,pi*)) in azide 1a are almost degenerate, at approximately 74 and 76 kcal/mol above the ground state (S0), respectively.