60366-01-0Relevant articles and documents
Tertiary alkylations of aldehydes, ketones or imines using benzylic organoboronates and a base catalyst
Nagao, Kazunori,Nakamura, Kei,Ohmiya, Hirohisa,Sato, Yukiya,Yabushita, Kenya
, p. 1065 - 1069 (2020/11/09)
The KHMDS-catalyzed tertiary alkylation of aldehydes, ketones or imines using tertiary benzylic organoboronates is reported. This protocol permitted the use of tertiary benzylic alkylboronates as the tertiary alkyl anion for construction of highly congested contiguous sp3 carbon centers. The mild and transition-metal-free reaction conditions are attractive features of the protocol.
Phosphonate-Directed Catalytic Asymmetric Hydroboration: Delivery of Boron to the More Substituted Carbon, Leading to Chiral Tertiary Benzylic Boronic Esters
Chakrabarty, Suman,Takacs, James M.
, p. 10530 - 10536 (2018/10/25)
Phosphonate-directed catalytic asymmetric hydroboration (CAHB) of β-aryl/heteroaryl methylidenes and trisubstituted alkenes by pinacolborane enables facile access to functionalized, chiral tertiary benzylic boronic esters. Hydroboration is catalyzed by a chiral rhodium catalyst prepared in situ from a Rh(I) precursor in combination with a simple TADDOL-derived chiral cyclic monophosphite in a 1:1 ratio. The regio- and stereochemistry arise from the combined effects of the relative disposition of the directing group to the alkene, the alkene substitution pattern, and the necessity of an aryl substituent attached to the alkene. A range of aryl and heteroaryl substituents can be accommodated, and for several chiral substrates, the reactions are efficiently catalyst-controlled, enabling the choice of diastereomeric products as desired. Stereospecific transformations of the chiral boronic ester afford chiral phosphonates bearing a quaternary carbon stereocenter. The synthetic utility of the products is further demonstrated by α-oxidation of the phosphonate, leading to hydroxy- and oxophosphonates; the latter readily undergo elimination/substitution reactions to unmask the phosphonate functionality with the formation of aldehydes, alcohols, esters, amides, acids, and ketones.
Rhodium-catalyzed allylic substitution with an acyl anion equivalent: Stereospecific construction of acyclic quaternary carbon stereogenic centers
Evans, P. Andrew,Oliver, Samuel,Chae, Jungha
, p. 19314 - 19317 (2013/02/21)
A highly regio- and stereospecific rhodium-catalyzed allylic alkylation of tertiary allylic alcohol derivatives with a cyanohydrin pronucleophile is described. This direct and operationally simple protocol provides a fundamentally novel approach toward the synthesis of α-quaternary substituted ketones and circumvents many of the inherent problems associated with conventional enolate alkylation reactions. The stereospecific variant of this reaction provides the enantiomerically enriched α-quaternary substituted allylic aryl ketone, which is a particularly challenging intermediate for more conventional enolate-based strategies.
