Sulfonamides, homoallylic

Difluoromethyl proline has been prepared by a related approach. Synthesis of cis- and fra 5-4-trifluoromethyl-D-prolines has been performed starting from the Garner aldehyde. 4-Trifluoromethyl, difluoromethylene, or difluoromethyl prolines could also be prepared by 5-endo-trig cyclization of A-(homoallyl)-sulfonamides. ... 

Solvolysis of Diels-Alder adducts provides a useful means of preparing a variety of nitrogen-containing compounds. For instance, the hydrolysis of A Cbz or A -Ts bicylic sulfonamides 44 and 112 with NaOH affords the homoallylic carbamate 113 and sulfonamide 114, respectively (Scheme 12) <2000TL3743, 2002TA2407>. Related hydrolysis reactions have also been reported with monocyclic 1,2-dihydrothiazine oxides <2004JOC7198>. 

Allylation of aldimines and sulfonimines with indium powder in poly(propylene) glycol (MW 1000), a benign and recyclable reaction medium, results in the formation of the corresponding homoallylic amines and sulfonamides in high yields (Equation (62)).265... 

Diastereoselective synthesis of homoallylic amines. The Diels-Alder adducts (2) formed from 1,3-dienes and 1 undergo basic hydrolysis to a single unsaturated sulfonamide (3) via a concerted rctro-cnc reaction. 

Carbonyl Allylation and Propargylation. Boron complex (8), derived from the bis(tosylamide) compound (3), transmeta-lates allylstannanes to form allylboranes (eq 12). The allylboranes can be combined without isolation with aldehydes at —78°C to afford homoallylic alcohols with high enantioselectivity (eq 13). On the basis of a single reported example, reagent control might be expected to overcome substrate control in additions to aldehydes containing an adjacent asymmetric center. The sulfonamide can be recovered by precipitation with diethyl ether during aqueous workup. Ease of preparation and recovery of the chiral controller makes this method one of the more useful available for allylation reactions. 

Allyiboron reagent R,R)-19S reacts with a variety of achiral aldehydes, affording homoallylic alcohols 240 in excellent yields and enantiomeric excess (Table 11-19). Corey rationalized that adducts 240 should arise through transition state 333. The alternative transition state, 334, is disfavored due to unfavorable steric interactions between the a-methylene group of the reagent and the adjacent sulfonamide ligand. Note that the toluene substituents of the sulfonamides in transition states 333 and 334 are spatially oriented so as to avoid steric interactions with the phenyl substituents of the chiral auxiliary. 

Generation of electrophilic halogen. The title reagent has found use in oxidation of KBr to initiate cyclization of homoallylic sulfonamides. The use of the p-anisyl congener to oxidize powdered KBr for benzylic bromination is also realized. 4-Aiylbutanoic acids are converted into y-aryl-y-butyrolactones by this method. ... 

This allylation protocol was used in the total synthesis of amphidinolide to give homoallylic alcohol 12 in 72% yield and 17 1 dr (eq 5). Initial transmetallation of stannane 10 with (R,R)-1 via allylic transposition yielded an intermediate borane. Introduction of aldehyde 11 at -78 °C provided for a facile condensation reaction leading to 12. Stereocontrol was induced from the 1,2-diphenylethane sulfonamide auxiliary and could be predicted from a Zimmerman-Traxler model with minimized steric repulsions. The high level of selectivity obtained in this case was a result of a matched diastereomeric transition state featuring the inherent Felkin-Ahn selectivity for nucleophilic attack in aldehyde 11, with the (5)-configuration of the benzoate of 10, as well as the (7 ,7 -antipode of auxiliary 1, resulting in threefold stereodifferentiation. 

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