Preparation and Reactions of Masked Allylic Organozinc Reagents

Abstract

Allylic zinc reagents have been prepared from sterically hindered homoallylic alcohols 10 and 13, using a novel fragmentation reaction of the corresponding zinc alkoxide, without any homocoupling products. These allylic zinc reagents react with a range of electrophiles in good to excellent yields. Substituted allylic zinc reagents have also been prepared in this manner. alpha-Substituted homoallylic alcohols 37, 46, and 51 give solely alpha-substituted products after the fragmentation-allylation sequence; these products are obtained not only regioselectively but also with extremely high anti diastereoselectivity. Likewise, gamma-substituted homoallylic alcohols 57 and 58, undergo the fragmentation-allylation reaction to give gamma-substituted products. The reaction has also been demonstrated to be catalytic in zinc salts.

Involvement of an Oxidation‐Reduction Equilibrium in Chromium‐Mediated Enantioselective Nozaki–Hiyama Reactions

“…Benzaldehyde (1a) was distilled from potassium hydride. Spectral data of the known compounds 4a, [23] 4b, [24] 5a, [23] 5b, [25] and 5c [5] were in accordance with the literature data. Benzyl alcohol was characterized by comparison with a commercially available sample.…”

Carbozincation Reactions of Carbon–Carbon Multiple Bonds

“…The fragmentation reaction of homoallylic alcohols allows the preparation of highly substituted and functionalized allylic zinc reagents. 163 Caution 51 Preparation of Rieke's activated zinc. A 50-mL 2-necked flask, fitted with a magnetic stirrer, an inert gas inlet, and a septum cap was charged with naphthalene (1.62 g, 12.66 mmol) and freshly cut lithium (84.9 mg, 12.23 mmol).…”

Synthesis of homoallylic amines and acylhydrazides by tin powder‐promoted multicomponent one‐pot allylation reactions

“…[9][10][11][12][13][14][15][16][17][18][19][20][21] As reported in the literature, allylic organometallics such as allylic Mg, [22,23] Zn, [24,25] In, [26][27][28][29] Sn, [30][31][32][33][34][35][36][37][38] Si, [39,40] B [25,41] and Sm [42,43] have been intensively investigated in allylation reactions. Among these organometallics, allylic stannanes have been widely used because of their easy availability, air and moisture stability, tolerance to functional groups and high selectivity.…”