B-allenyl- and B-(gamma-trimethylsilylpropargyl)-10-phenyl-9-borabicyclo[3.3.2]decanes: asymmetric synthesis of propargyl and alpha-allenyl 3-degree-carbinols from ketones |
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Authors: | Hernandez Eliud Burgos Carlos H Alicea Eyleen Soderquist John A |
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Affiliation: | University of Puerto Rico, Department of Chemistry, Rio Piedras, PR 00931-3346, USA. |
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Abstract: | Simple and efficient Grignard procedures are reported for the syntheses of B-allenyl-10-(phenyl)-9-borabicyclo[3.3.2]decane (1) and its B-(gamma-trimethylsilylpropargyl) counterpart (2) in both enantiomeric forms. Both add selectively to ketones, providing propargyl- and alpha-silylallenyl 3-degree-carbinols, respectively (i.e., 6 (61-93% ee) and 9 (64-98% ee)). The air-stable boron byproduct is efficiently recovered and recycled back to either 1 or 2. The ozonolysis and bromination of 9 provide nonracemic alpha-hydroxy acids and gamma-bromopropynyl carbinols, respectively. |
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