6H-Dibenzo[b,d]pyrans. I. Synthesis

1975 ◽  
Vol 53 (3) ◽  
pp. 343-349 ◽  
Author(s):  
John P. Devlin
Keyword(s):  
Carboxylic Acid ◽  
Sodium Borohydride ◽  
Boron Trifluoride ◽  
Boron Trifluoride Etherate ◽  
Ring Cleavage ◽  
Borohydride Reduction ◽  
Grignard Addition ◽  
Sodium Borohydride Reduction

The preparation of 2′,4′-dihydroxy- and 2′,6′-dihydroxybiphenyl-2-carboxylic acid lactones (3 and 4) is described. Grignard addition to or direct boron trifluoride etherate – sodium borohydride reduction of these lactones yields respectively these 6,6-substituted (e.g. 6) or the 6,6-unsubstituted (13a) 6H-dibenzo[b,d]pyrans. Evidence that the reductive route proceeds without ring cleavage is presented.

Nuclear analogs of β-lactam antibiotics. I. Synthesis of O-2-isocephams

1977 ◽  
Vol 55 (3) ◽  
pp. 468-483 ◽  
Author(s):  
Terrence William Doyle ◽  
Bernard Belleau ◽  
Bing-Yu Luh ◽  
Carrado F. Ferrari ◽  
Michael Patrick Cunningham
Keyword(s):  
Schiff Base ◽  
Carboxylic Acid ◽  
Total Synthesis ◽  
Sodium Borohydride ◽  
Boron Trifluoride ◽  
Cycloaddition Reaction ◽  
Phenoxyacetic Acid ◽  
Azido Group ◽  
Borohydride Reduction ◽  
Sodium Borohydride Reduction

The preparation by total synthesis of a saturated cephalosporin analog 7-β-phenoxyacet-amido-3-ethoxy-O-2-isocepham-4-α-carboxylic acid 30, is described. Compound 30 was prepared via cycloaddition of azidoacetyl chloride to the cinnamylidene Schiff base of ethyl 2-amino-3, 3-diethoxypropionate 13b to give the cis-3-azido-4-styryl β-lactam 15b. Ozonolysis of 15b followed by sodium borohydride reduction gave the alcohol 18b. Boron trifluoride treatment of 18b gave ethyl 7-β-azido-3- β-ethoxy-O-2-isocephem-4-carboxylate 27. Reduction of the azido group followed by coupling with phenoxyacetic acid and saponification of the ester gave 30. The mechanism of the cycloaddition reaction and the stereochemical assignments are also discussed.

1,2-Benzothiazines. II. The Preparation and Sodium Borohydride Reduction of 3-Acyl-2H-1,2-benzothiazin-4(3H)-one 1,1-Dioxides1

1965 ◽  
Vol 30 (7) ◽  
pp. 2241-2246 ◽  
Author(s):  
Harold Zinnes ◽  
Roger A. Comes ◽  
Francis R. Zuleski ◽  
Albert N. Caro ◽  
John Shavel
Keyword(s):  
Sodium Borohydride ◽  
Borohydride Reduction ◽  
Sodium Borohydride Reduction
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