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DOI: 10.1055/s-0034-1378618
Bis(2-aminobenzoimidazole)-Organocatalyzed Asymmetric Alkylation of Activated Methylene Compounds with Benzylic and Allylic Alcohols
Publikationsverlauf
Received: 15. Juli 2014
Accepted: 18. Juli 2014
Publikationsdatum:
04. September 2014 (online)
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Abstract
The first organocatalyzed asymmetric alkylation of activated methylene compounds using benzylic and allylic alcohols as alkylating agents through dual hydrogen bond activation in an SN1-type reaction is reported. This green protocol employs a bis(2-aminobenzoimidazole) in combination with an achiral Brønsted acid as a bifunctional catalytic system and gives the alkylation products with moderate to good enantioselectivities. Although the scope of the reaction is limited, this methodology can be considered as complementary to existing metal-catalyzed processes. In addition, modest results were obtained in a first attempt to perform a metal-free asymmetric Tsuji–Trost reaction using allylic alcohols. Finally, the recovery and reusability of the organocatalyst is also achieved.
Supporting Information
- for this article is available online at http://www.thieme-connect.com/products/ejournals/journal/ 10.1055/s-00000084.
- Supporting Information
-
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For recent selected examples, see:
For recent contributions from our group about allylic substitution using free alcohols as alkylating agents, see:
For selected recent publications from our group dealing with the use of activated methylene compounds in enantioselective reactions, see:
The E values (electrophilicity parameters in Mayr’s scale) are related with carbocation stability and hence with the reactivity. Thus, lower E value implies higher stability and lower reactivity. E (1a +) = –7.02; E (1b +) = +0.47; E (1d +) = 0; E (4a) = +2.70; E (4b) = –1.45. Extracted from:
For selected reviews on this topic, see:
For recent reviews about the use of free allylic alcohols in enantioselective processes, see: