Alkylations of Enols and Enolates

C‐Alkylation of Ketones and Related Compounds by Alcohols: Transition‐Metal‐Catalyzed Dehydrogenation

“…Under the reaction conditions shown in Scheme 13, the b-CF 3 -substituted secondary (R)-allylic alcohol bearing ab romophenyl moiety (97 % ee)w as fully converted into the saturated (R)-ketone [94 % ee;E q. (22)]. [70] Thes ynthetic protocol provides an alternative route to the asymmetric synthesis of the CF 3 analogues of citronellol.…”

“…Carbon-carbon bond formation by means of efficient, selective,a nd environmentally benign processes has been achallenging task in synthetic chemistry. a-Alkylation of the enolates of ketones with electrophilic alkylating agents was documented to construct aC À Cbond, [7,21,22] but this protocol suffers from the production of stoichiometric amounts of undesirable salts as waste.In2001, Shim, Cho,and co-workers reported ruthenium-catalyzed transfer hydrogenation of ketones with primary alcohols accompanied by CÀCb ond formation. [23] Later,C ho documented the ruthenium-catalyzed b-alkylation of secondary alcohols with primary alcohols.…”

Studies culminating in the total synthesis and determination of the absolute configuration of (−)-saudin

“…Attempted alkylation of (-)- 75 with LDA followed by addition of excess MeI, under a variety of reaction conditions, led to mixtures of 76α and 76β and 74 along with unreacted (-)- 75 , even when excess of LDA was used. Reasoning that diisopropyl amine could enhance the proton exchange between the starting lactone enolate and 76α/β leading to epimerization and polyalkylation, 34 we decided to use the more hindered and stronger base Li-TMP, which is known to reduce the formation of aggregates. 35 Our hypothesis was confirmed when complete conversion of 75 was observed and a kinetically controlled mixture of 76 ( 76α / 76β ~1:1.5) was isolated in 75% yield accompanied by only traces of 77 .…”

The Stereoselective Synthesis of the Nonnatural Enantiomers of Communiols A-C. A Stereochemical Correction

“…13 C NMR: 9.9 (CH 3 ), 14.1 (CH 3 ), 26.3 (CH 2 ), 33.7 (CH 2 ), 35.5 (CH 2 ), 38.1 (CH), 60.1 (CH 2 ), 72.6 (CH 2 ), 75.0 (CH), 81.3 (CH), 122.6 (CH), 146.4 (CH), 166.2 (C) : C,64.44;H,9.15. Found C,64.55;H,9.10.…”

“…Sharpless dihydroxylation [8] of the latter gave the expected γ,δ-dihydroxy ester, which then spontaneously cyclized to 11. Protection as the TBS (t-butyldimethylsilyl) derivative was followed by αallylation via the lithium enolate [9]. The reaction took place with a very good stereoselectivity and provided lactone 10 as a 92:8 diastereomeric mixture (83% yield of 10 after chromatographic separation).…”