Isopropyl iodide, photolysis

The photolysis of isopropyl iodide has been investigated by McMillan and Noyes.16 Addition of excess NO increased the quantum yield of iodine formation at 3130 A. to — 0.5, and in the presence of metallic silver the quantum yield of photodecomposition rose to unity. Hence the primary process at 3130 A. is exclusively... 

Prototypical radical additions were examined under manganese-mediated photolysis conditions with InCp as the Lewis acid, coupling isopropyl iodide with a variety of y-hydrazonoesters 35a-35d (Table 6) bearing varied substitution at the position a to the ester. The a-methyl, a,a-dimethyl, and a-benzyloxy substituents appeared to have little effect on reaction efficiency and selectivity, as all provided the isopropyl adducts with consistently high diastereoselectivities and excellent yields (91-98%). Surprisingly, the selectivity was only slightly... 

Photolysis of Isopropyl Iodide in the Presence of Oxygen (McMillan86) ... 

Hot isopropyl radicals are believed to be formed by the photolysis of isopropyl iodide as with methyl iodide.189... 

In an attempt to detect alkyl radicals spectroscopically, Thrush168 carried out the flash photolysis of ethyl, propyl, and isopropyl iodides... 

The lack of laser action in the photolysis of isopropyl iodide raises intriguing questions. As Husain and Donovan point out, this does not necessarily indicate the absence of population inversion, since under the laser experimental conditions there could instead be an insufficient absolute concentration of I atoms. Spectroscopic studies show that excited iodine atoms are produced from isopropyl iodide photodissociation, but at lower relative concentrations than for n-propyl iodide under similar conditions. Since the two propyl iodides show similar I quenching rates, it would appear most likely that a decreased I /I ratio is the reason stimulated emission is not seen. The present experiments, unfortunately, cannot provide a more quantitative explanation. The distinct broadness of the isopropyl iodide distribution in fig. 2 indicates a departure from the methyl- ethyln-propyl trend, and might represent comparable amounts of P and I atom production, with overlapping translational energy distributions, at least when viewed with our present... 

Similar observations have been made with isopropyl iodide for which the main hydrocarbon photolysis products are propane, propene and 2,3-dimethyl-butane. 

Other photolysis studies have been reported for ethyl iodide -propyl iodide and isopropyl iodide in the gas phase, and also in liquid and solu-tion . Solution and liquid phase studies have also been reported for butyl ° , pentyl and cetyl iodides ". The primary process in the photolysis of alkyl iodides has been further discussed by Donovan and Husain in reference to the formation of excited halogen atoms. 

For synthesis of a alkoxy y amino acid 43, nonbasic conditions would be a necessity, considering the potential for (3 elimination of the alkoxy group from the hydrazone precursor 45 (Scheme 2.7). Flere, the addition of isopropyl iodide under the Mn mediated photolysis conditions afforded 46 as a single diastereomer in 77% yield, without any evidence of (3 elimination. 

The first efforts to address this issue involved hydrazone ( ) 62 (Scheme 2.9), prepared as a mixture E/Z 92 8) and separated via flash chromatography as the pure ( ) isomer in 75% yield. In this preparation, the oxazolidinone N amination was accomplished using a solution of monochloramine in methyl tert butyl ether [45], furnishing a quantitative yield of the N amino 2 oxazolidinone, which in turn was condensed with methyl pyruvate to afford 62. Addition of ethyl iodide to ( ) 62 using the Mn mediated photolysis conditions as described above gave 66% yield ofthe ethyl adduct, with a modest diastereomer ratio of 70 30, while the correspond ing isopropyl addition was very effective (85% yield, dr 92 8). Variation in the stoichiometry indicated that amounts less than 2 equiv of Lewis acid proportionally lowered the diastereoselectivity, suggesting that, in this case, the ester may participate... 

---