Propargylation of carbonyl compounds: An efficient method for the synthesis of homopropargyl alcohols

Unexpected Propargylic Retro-Brook Rearrangements in Alkynes

“…In contrast, the propargyl anion in 12 is stabilized by the allene resonance form, and consequently, the reaction is no longer thermodynamically favored. The structure and reactivity of propargyl/allenyl dianions, such as 10 , are only rarely exploited in synthesis, and to the best of our knowledge this is the first attempt to investigate its structure by means of DFT calculations. Our studies demonstrate that the generation of the propargyl/allenyl dianion could be used as a method to enhance the reactivity of the propargylic position of alkynes.…”

Zn Mediated Regioselective Barbier Reaction of Propargylic Bromides in THF/aq. NH4Cl Solution

“…In our investigation we chosed 1-bromo-2-propyne and 1-bromo-2-nonyne as two model compounds that would react preferentially as the corresponding propargyl or allenyl metal derivatives in Barbier reactions [ 8 ]. A mixture of anhydrous THF and saturated aqueous NH 4 Cl solution was used as solvent.…”

“…The Barbier reaction has been successfully applied recently in the preparation of new β-lactam antibiotics [ 3 ], in propargylation of cyclic imides [ 4 ], in asymmetric allenylation of aliphatic aldehydes catalyzed by a chiral formamide [ 5 ] and for the synthesis of propargylic and allenic alcohols [ 6 , 7 ]. A mechanism for the Barbier reaction has also been proposed ( Scheme 1 )[ 8 ]:…”

Regiospecific Palladium-Catalyzed Cross-Coupling Reactions Using the Operational Equivalent of 1,3-Dilithiopropyne

“…Later we showed that dianion 6 reacted regiospecifically with aromatic aldehydes and ketones to produce, after protonolysis, the corresponding homopropargyl alcohols, without contamination with the allenic isomers, in very good yields. 29 Since the high price of allene 7 considerably discourages the use of this methodology, we later developed a more economical procedure 30 to prepare 1,3-dilithipropyne dianion 6 by treatment of propargyl bromide 8 with n-BuLi in the presence of TMEDA (Scheme 2, Method B). Treatment of dianion 6 with aldehydes and ketones produced the corresponding homopropagyl alcohols in excellent yields.…”