Steroide. 73. Gekoppelte Additionsreaktionen an 14,15‐ungesättigten Androstanen Einfluß des positiven Halogens auf die Regioselektivität

Abstract

Steroids. 73. Joint Addition Reactions to 14,15‐Unsaturated Androstanes. Influence of the Positive Charged Halogen on the Regioselectivity The joint addition of positive charged halogens and nitrogenous nucleophils to 14,15‐unsaturated olefins is investigated. It was established that the regioselectivity of the addition reaction is different for bromine and iodine. This surprising result is discussed. Ring closure reactions of the addition products to the corresponding aziridines are investigated.

Steroids: reactions and partial syntheses

“…A free-radical pathway has been suggested for the irradiated reaction.34 Whereas iodine azide (from Niodosuccinimide and hydrazoic acid) reacts with the A14compound (31) to give the 14a-azido-1 Sa-iodo-compound (32), which is reduced by lithium aluminium hydride to the 14P, 1 Sgepimino-compound (33), the reaction of the same olefin with Nbromosuccinimide and hydrazoic acid gives the 1 Sa-azido-14Pbromo-compound (34). The latter is converted (by triethyl phosphite followed by lithium aluminium hydride) into the 14a, 15a-epimine (35). Similar results were obtained by using cyanamide with the N-halogeno-imides (giving, after treatment of the products with potassium bicarbonate, the N-cyanoepimines) or by using cyanic acid and the N-hal~geno-imides.~~ The difference has been explained in terms of an ionic mechanism for the reactions of N-iodosuccinimide and a radical one for the reactions of N-bromosuccinimide.…”

Utilization of bromine azide to access vicinal-azidobromides from arylidene malononitrile

“…Subsequently, Hassner and co-workers [4][5][6][7][8] made a major contribution to understanding the mechanism of halogen azide addition to olefins and its regiospecificity through two different pathways, namely a radical or an ionic process. Also, BrN 3 was synthesized by many in situ systems starting from [Br 2 gas/NaN 3 ] which was modified by Hassner to [Br 2 -HCl-NaN 3 ] [3-5], hydrazoic acid [NXS−HN 3 , X = I, Br] [9] and [Br 2 /NaN 3 in base] [10]. However, most of these methods have significant hazards related to explosivity and toxicity.…”

Taming Chlorine Azide: Access to 1,2-Azidochlorides from Alkenes

“…Consistent with the higher oxidation potential of bromine, the published chemistry of bromine azide is less extensive than that of iodine azide. BrN 3 was first synthesized from Br 2 gas and solid NaN 3 , which was modified by Hassner [Br 2 –HCl–NaN 3 ] ,, into a somewhat hazardous procedure that nevertheless achieved some subsequent use. − Other approaches have involved the in situ generation of toxic and explosive hydrazoic acid [NXS–HN 3 , X = I, Br]; , the use of Br 2 solution in the presence of sodium azide under neutral or basic conditions , avoids that particular hazard, albeit with diminished yields and the formation of other side products. The accessibility and versatility of the technique reported by Krief in 1974 [NBS–NaN 3 ] , was noted by several groups, − and other recently published protocols still rely on NBS as the most common bromine source [NBS–TMSN 3 ] .…”