In the late eighties, Chatgilialoglu and coworkers introduced tris(trimethylsilyl)silane, (TTMSS or — Organic Chemistry Chemistry Question
Tris(trimethylsilyl)silane and azobisisobutyronitrile
In the late eighties, Chatgilialoglu and coworkers introduced tris(trimethylsilyl)silane, (TTMSS or (TMS)3SiH) as a radical-based reducing agent for functional group modifications and a mediator for sequential radical reactions. The use of (TMS)3SiH allows reactions to be carried out under mild conditions with excellent yields of products and remarkable chemo-, regio-, and stereoselectivity. (TMS)3SiH is an effective reducing agent for the removal of a variety of functional groups. Examples of dehalogenation (Cl, Br and I) and reductive removal of chalcogen groups (SR and SeR) are well known. The most popular thermal initiator is azobisisobutyronitrile, {AIBN, [(CH3)2C(CN)]2N2} under heating conditions in toluene.
I. Reactions using TTMSS and AIBN are given in the hereunder examples.
1. Radical cyclisation was studied using two different reducing agents: tributyltin hydride (TBTH, Bu3SnH) and tris(trimethylsilyl)silane (TTMSS).
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2. Radical introduction of a side chain (alkylation)
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II. TTMSS has found multiple applications in the organic synthesis described in the below reactions:
3. The compound (I) was converted to B and C via the radical intermediate A.
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4. The compound (II) was converted to D.
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5. The compound (III) was converted to E, and then through several steps to afford (±) - vindoline
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6. Horsfiline (J) is an oxindole alkaloid found in the plant Horsfieldia superba, which has analgesic effects. The method for horsfiline synthesis from the compound (IV) was described below:
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Write down the structural formulae of all compounds A to I in the above reactions.
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A, B and C from the compound (I):
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From the compound (II):
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E from the compound (III):
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I from the compound (IV) through radicals F and G:
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F represents the acyclic radical formed by addition of the aryl radical to the terminal alkene; G represents the cyclic nitrogen-radical intermediate; I represents the pyrrolidinyl-indoline core intermediate formed after the extrusion of N2, which undergoes subsequent N-methylation to afford (+/-)-Horsfiline (J).