Flash vacuum thermolysis (FVT) of the same α-oxo diazo ketone 14 at 650 °C gave the same ketene, isolated in Ar matrix at 12 K. ... 2. Tetramerization of 16 to 1,3'-tetrakis(indolylmethanone ) (20). Isolation of ketene 16 at 12 K and subsequent warmup revealed that this ketene is only stable below 58 K. This instability is due to the imine function which acts as a nucleophile toward another ketene molecule. 18 IR spectroscopy showed that the product of this thermal ...