An improved method for the use of acetal-substituted Grignard reagents in organic synthesis

Abstract

Grignard reagents derived from 2-(3-chloropropyl) -1,3-dioxolan (1 ) and 2-(3-chloropropyl) -5,5-dimethyl-l.3dioxan (2) can be prepared in high yield without decomposition. They undergo 1 ,Z-addition to acrylaldehyde to give allylic alcohols (4a and b), which can be oxidized t o give monoprotected dicarbonyl compounds.

Synthesis of spiroacetal-triazoles as privileged natural product-like scaffolds using “click chemistry”

“…, 412 (M − OSiMe 2 t Bu, 100), 343 (M − OSiPh 2 t Bu, 11), 211 (27), 197 (16), 149 (20), 135 (24), 121 (36), 99 (40), 91 (20), 78 (37), 73 (94).…”

Concise Total Synthesis of Enigmazole A

“…[17] Other procedures were less productive.Attachment of aBoc-group then allowed the chiral information to be relayed to aterminal epoxide.T othis end, the double bond in 10 was activated with IBr and the resulting product 11 was treated with K 2 CO 3 in MeOH to cleave the cyclic carbamate and close the oxirane ring. [18,19] Ac opper-catalyzed opening of the epoxide in 12 with the functionalized Grignard reagent 13, [20] in concert with routine protecting group management, led to 15 which was endowed with the necessary orthogonal silyl ethers.…”

A Stereoselective Synthesis of Lentiginosine

“…Acetal-substituted Grignard reagents can difficult to be prepare; accordingly, the well-known Grignard reagent 9 derived from 2-(3-chloropropyl)-5,5-dimethyl-1,3-dioxan ( 8 ) was chosen to establish the feasibility of the novel synthetic approach. The chloroacetal 8 is readily available in large scale by a two-step procedure employing 2,3-dihydrofuran and 2,2-dimethyl-1,3-propanediol as inexpensive starting materials (65% overall yield) .…”