Reactivite des propargyl- et allenyl-boronates de dibutyle vis-a-vis des derives carbonyles III. Stereochemie de la condensation sur les aldehydes

General Method for Preparation of Allenic Zinc Reagents by Three-Carbon Homologation of Triorganozincates: Convergent Three-Component Coupling of Propargylic Substrates, Triorganozincates, and Electrophilic Reagents

“…The reaction with benzaldehyde exhibited a notably low level of stereoselectivity (entry 5). A similar anomaly of benzaldehyde has been observed elsewhere. 13a, High synthetic utility of the present one-pot reactions is also exemplified in application to the synthesis of highly functionalized homopropargylic alcohols such as 14p , 14s , and 14t .

4

…”

A New Diastereodivergent Synthesis of 1,2-Disubstituted Homopropargylic Alcohols

“…[15] The synthesis. They are key intermediates in the synthesis of use of allenylboron, [16] chromium, [17] magnesium, [18] and tierythronolide B, [1] neomethynolide [2] and oudemansin C, [3] tanium [19] reagents leads generally to a lower regioselectiv-N-BOC ADDA, [4] [5] and maytansinol [6] as well as in some ity or stereoselectivity. approaches to milbemycins [7] and avermectins.…”

Allenylzinc reagents: new trends and synthetic applications

“…[11][12][13][14] Reactions of allenylmetals with aldehydes have been well studied and require a proper choice of the metal to obtain good regioselectivity and stereoselectivity. For example, the use of allenylzinc, [15][16][17][18] allenyltin 19 and allenylindium 15 has been reported to show total control of the regio-and stereoselectivity, whereas the use of allenylboron, [20][21][22] chromium, 23 magnesium 24,25 and titanium 26 reagents leads generally to lower regio-and stereoselectivity. However reactions using propargylic carbenoids are not well developed and a limited number of examples have been reported, such as a,adifluoropropargylzinc, 27 and propargylindium carbenoids [28][29][30][31][32] as have a,a-dichloropropargyllithium, 33 a,a-dichoropropargylpotassium, 34 lithiated a,a-difluoropropargylphosphonate, 35 and heterocuprate carbenoids.…”