A Regio-and Stereo-Specific Addition of Iodine Azide to C-9 and C-13 Cyclic Allenes

S Narayana Moorthy and Devadas Devaprabhakara

Department of Chemistry, Indian Institute of Technology, Kanpur 208016, India.

Iodine azide is known to undergo addition to alkenes and alkynes with a remarkable high degree of regio- and stereoselectivity¹. However, there are no reports of such additions of iodine azide to allenes. In this Communication a regio- and sterospecific addition of iodine azide to 1, 2-cyclodecadiene and 1, 2-cyclotridecadiene is described. The results are summarized in the Table.

Table : Addition of IN3 to C-9 and C-13 cyclic allenes.

Cyclic Allene Product2 Percentage Yield
1,2 – Cyclononadiene 3-Azido-2-iodo-cis-cyclononene 65
1,2 – Cyclotridecadiene 3-Azido-2-iodo-trans-cyclotridecene 72

Iodine azide was prepared in situ in the manner described by Hassner and coworkers3 by addition of iodine monochloride (9.1 g, 0.055 mol) to a stirred slurry of sodium azide (7.5g, 0.125 mol) at ca -10°C in acetonitrile (50cm³). Allene (0.06 mol) in acetonitrile (10cm³) was added slowly over a period of 0.5 h and stirred for 15 h at room temperature. Normal work-up procedure followed by chromatography over neutral alumina gave 1:1 pure liquid adducts.
The results suggest that the addition of IN3 to C-9 and C-13 cyclic allenes is not only regiospecific but also stereospecific. Any one of the following possible reaction intermediates (I-III) could explain the regiospecificity of the addition. However, the authors feel strongly that the stereospecificity of the addition could be explained better via the resonance stabilized planar allylic cation (I). In that event, the stereochemistry of the adduct from C-9 or C-13 cyclic allene must be dictated by the stability of (I).

At present, work is in progress with acyclic allenes, and also optically active cyclic allene to check the validity of this proposal.

The C.S.I.R., New Delhi, is thanked for an award of a S.R.F. to S.N.M., and Dr P. Balram, Carnegie Mellon University, Pittsburg, Pennsylvania, USA, for measurement of the 250MHZ 1H n.m.r. spectra.

References

  1. Hassner, A., Accounts Chem.Res., 1971, 4, 9.
  2. The identity of the products was established by elemental analysis, ¹H.n.m.r. and infrared spectral measurements.
  3. Fowler, F.W., Hassner, A. & Levy, L.A., J. Am. chem. Soc., 1967, 89, 2077.