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Why will Boc get cleaved under acidic conditions while Alloc does not? Can Alloc somehow be resonance stabilized? If so, how? Any help would be appreciated.

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user21398
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    All else being equal, t-Bu carbocation is easier to form than allyl carbocation (see https://chemistry.stackexchange.com/a/87701/16683); so the easiest explanation may be "carbocation stability", although "stability" needs to be carefully defined here: let's say $\Delta E$ for the reaction $\ce{R2NCO2X + H+ -> R2NCO2H + X+}$, where X = allyl or t-Bu. (Of course, $\ce{R2NCO2H}$ will decompose to $\ce{R2NH + CO2}$, but the energetic contribution there is independent of X.) – orthocresol Jun 26 '21 at 23:24
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    Your original assertion that Alloc will not get cleaved by acidic conditions is incorrect. If you look at the reactivity charts in Greene' s "Protective Groups in Organic Synthesis" the reactivity of Alloc is very similar to tBoc. It is merely that acid condition are not routinely used in the literature for Alloc removal – Waylander Jun 27 '21 at 10:18
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    @Waylander The "more acid-stable" was given as an explanation in an organic chemistry workbook which discussed the total synthesis of Minfiensine by Overman and colleagues (Overman 2005). Quote directly from the Overman paper: "Because of the propensity of the aminal fragment to open under acidic conditions, the tert-butoxycarbonyl (Boc) protecting group had to be exchanged for an allyloxycarbonyl (Alloc) group prior to transforming the epoxide to an allylic alcohol." Indeed, they did not deprotect Alloc with acid later in the synthesis, but with Pd-catalyzed Tsuji–Trost reaction – user21398 Jun 27 '21 at 15:05
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    It would be worthwhile to include this context, including a link to the paper, in your original question by [edit]ing it. – orthocresol Jun 27 '21 at 16:20
  • @orthocresol Will do when I have the time soon. – user21398 Jun 27 '21 at 20:31
  • Did Overman state what conditions the Alloc survived that cleaved the tBoc? As @orthocresol states tBoc is more readily cleaved by acid because of the greater stability of the tBu cation. The allyl cation is also reasonably stable so will Alloc also cleave in acid conditions. With this difference in cation stabilities it may be possible with careful selections of conditions to differentiate between them, but I would not expect Alloc to be stable to std tBoc cleavage conditions such as TFA/DCM or HCl/EtOAc – Waylander Jun 27 '21 at 22:24

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